ON WIRING, CONNECTING UP, AND LOCALISING FAULTS.
[S] 66. However good may be the bells, indicators, batteries, etc., used
in an electric bell installation, if the _wiring_ be in any wise faulty,
the system will surely be continually breaking down, and giving rise to
dissatisfaction. It is therefore of the highest importance that the
workman, if he value his good name, should pay the greatest attention to
ensure that this part of his work be well and thoroughly done. This is
all the more necessary, since while the bells, batteries, relays,
pushes, etc., are easily got at for examination and repair, the wires,
when once laid, are not so easily examined, and it entails a great deal
of trouble to pull up floor boards, to remove skirtings etc., in order
to be able to overhaul and replace defective wires or joints. The first
consideration of course, is the kind and size of wire fitted to carry
the current for indoor and outdoor work. Now this must evidently depend
on three points. 1st, The amount of current (in amp[e']res) required to
ring the bell. 2nd, The battery power it is intended to employ. 3rd, The
distance to which the lines are to be carried. From practical
experience I have found that it is just possible to ring a 2-1/2" bell
with 1/2 an amp[e']re of current. Let us consider what this would allow
us to use, in the way of batteries and wire, to ring such a bell. The
electro-motive force of a single Leclanch[e'] cell is, as we have seen
at [S] 38, about 1.6 volt, and the internal resistance of the quart
size, about 1.1 ohm. No. 20 gauge copper wire has a resistance of about
1.2 ohm to the pound, and in a pound (of the cotton covered wire) there
are about 60 yards. Supposing we were to use 60 yards of this wire, we
should have a wire resistance of 1.2 ohm, an internal resistance of 1.1
ohm, and a bell resistance of about 0.1 of an ohm, altogether about 2.4
ohms. Since the E.M.F. of the cell is 1.6 volt, we must divide this by
the total resistance to get the amount of current passing. That is to
say:--
Ohms. Volts. Amp[e']res.
2.4) 1.60 (0.66,
or about 2/3 of an amp[e']re; just a little over what is absolutely
necessary to ring the bell. Now this would allow nothing for the
deterioration in the battery, and the increased resistance in the
pushes, joints, etc. We may safely say, therefore, that no copper wire,
of less diameter than No. 18 gauge (48/1000 of an inch diameter) should
be used in wiring up house bells, except only in very short circuits of
two or three yards, with one single bell in circuit; and as the
difference in price between No. 18 and No. 20 is very trifling, I
should strongly recommend the bell-fitter to adhere to No. 18, as his
smallest standard size. It would also be well to so proportion the size
and arrangement of the batteries and wires, that, at the time of setting
up, a current of at least one amp[e']re should flow through the entire
circuit. This will allow margin for the weakening of the battery, which
takes place after it has been for some months in use. As a guide as to
what resistance a given length of copper wire introduces into any
circuit in which it may be employed, I subjoin the following table of
the Birmingham wire gauge, diameter in 1,000ths of an inch, yards per
lb., and resistance in ohms per lb. or 100 yards, of the wires which the
fitter is likely to be called upon to employ:--
------------------------------------------------------------
Table of Resistance and lengths per lbs.
& 100 yards of cotton covered copper wires.
------------------------------------------------------------
Birmingham | Diameter in | Yards | Ohms. | Ohms. per
Wire Gauge. | 1000th of | per lb. | per lb. | 100 yards.
| an inch. | |
------------+-------------+----------+----------+-----------
No. 12 | 100 | 9 | 0.0342 | 0.0038
14 | 80 | 15 | 0.0850 | 0.0094
16 | 62 | 24 | 0.2239 | 0.0249
18 | 48 | 41 | 0.6900 | 0.0766
20 | 41 | 59 | 1.2100 | 0.1333
22 | 32 | 109 | 3.1000 | 0.3444
------------------------------------------------------------
[S] 67. Whatever gauge wire be selected, it must be carefully insulated,
to avoid all chance contact with nails, staples, metal pipes or other
wires. The best insulation for wires employed indoors is gutta-percha,
surrounded with a coating of cotton wound over it, except only in cases
when the atmosphere is excessively dry. In these, as the gutta-percha
is apt to crack, india-rubber as the inner coating is preferable. If No.
18 wire be used, the thickness of the entire insulating coating should
be thick enough to bring it up to No. 10 gauge, say a little over 1/10th
inch in diameter. There is one point that will be found very important
in practice, and that is to have the cotton covering on the wires
_leading_ to the bells of a different colour from that on the _return_
wires; in other words, the wires starting from the zinc poles of the
battery to the bells, indicators, relays, etc., should be of a different
colour from that leading from the carbon poles to the bells, etc.
Attention to this apparently trifling matter, will save an infinite
amount of trouble in connecting up, repairing, or adding on fresh branch
circuits. For outdoor work, wire of the same gauge (No. 18) may
generally be used, but it must be covered to the thickness of 1/10" with
pure gutta-percha, and over this must be wound tape served with
Stockholm tar. Wires of this description, either with or without the
tarred tape covering, may be obtained from all the leading electricians'
sundriesmen. Many firms use copper wire _tinned_ previous to being
insulated. This tinning serves two good purposes, 1st, the copper wire
does not verdigris so easily; 2ndly, it is more easily soldered. On the
other hand, a tinned wire is always a little harder, and presents a
little higher resistance. Whenever wires are to be joined together, the
ends to be joined must be carefully divested of their covering for a
length of about three inches, the copper carefully cleaned by scraping
and sand-papering, twisted tightly and evenly together, as shown in
Fig. 73 A, and soldered with ordinary soft solder (without spirits), and
a little resin or composite candle as a flux. A heavy plumber's
soldering iron, or even a tinman's bit, is not well adapted for this
purpose, and the blowpipe is even worse, as the great heat melts and
spoils the gutta-percha covering. The best form of bit, is one made out
of a stout piece of round copper wire 1/4" thick with a nick filed in
its upper surface for the wire to lie in (see Fig. 73 B). This may be
fastened into a wooden handle, and when required heated over the flame
of a spirit lamp. When the soldering has been neatly effected, the waste
ends _a_ and _b_ of the wire should be cut off flush. The wire must then
be carefully covered with warm Prout's elastic or softened gutta-percha,
heated and kneaded round the wire with the fingers (moistened so as not
to stick) until the joint is of the same size as the rest of the covered
wire. As a further precaution, the joints should be wrapped with a layer
of tarred tape. Let me strongly dissuade the fitter from ever being
contented with a simply twisted joint. Although this may and does act
while the surfaces are still clean, yet the copper soon oxidises, and a
poor non-conducting joint is the final result.
"That'll do" will not do for electric bell-fitting.
[Illustration: Fig. 73.]
[S] 68. Whenever possible, the wiring of a house, etc., for bell work,
should be done as soon as the walls are up and the roof is on. The
shortest and straightest convenient route from bell to battery, etc.,
should always be chosen where practicable to facilitate drawing the wire
through and to avoid the loss of current which the resistance of long
lengths of wire inevitably entails. The wires should be run in light
zinc tubes nailed to the wall.
In joining up several lengths of tubing, the end of one piece of tube
should be opened out _considerably_ of a trumpet shape for the other
piece to slip in; and the end of this latter should also be _slightly_
opened out, so as not to catch in the covering of any wire drawn through
it. The greatest care must be exercised in drawing the wires through the
tubes or otherwise, that the covering be not abraded, or else leakage at
this point may take place. In cases where tubes already exist, as in
replacing old crank bells by the electric bells, the new wires can be
drawn through the tubes, by tying the ends of the new wire to the old
wire, and carefully pulling this out, when it brings the new wire with
it. Or if the tubes are already empty, some straight stout wire may be
run through the tubes, to which the new wires may be attached, and then
drawn through, using, of course, every possible precaution to avoid the
abrasion of the insulating covering of the wire, which would surely
entail leakage and loss of current. All the old fittings, cranks,
levers, etc., must be removed, and the holes left, carefully filled with
dowels or plaster. In those cases where it is quite impossible to lay
the wires in zinc or wooden tubes (as in putting up wires in furnished
rooms already papered, etc.), the wires may be run along the walls, and
suspended by staples driven in the least noticeable places; but in no
case should the two wires (go and return) lie under the same staple, for
fear of a short circuit. It must be borne in mind that each complete
circuit will require at least two wires, viz., the one leading from the
battery to the bell, and the other back from the bell to the battery;
and these until connection is made between them by means of the
"contact" (pull, push, or key) must be perfectly insulated from each
other. In these cases, as far as possible, the wires should be laid in
slots cut in the joists under the floor boards, or, better still, as
tending to weaken the joists less, small holes may be bored in the
joists and the wires passed through them; or again, the wires may be led
along the skirting board, along the side of the doorpost, etc., and when
the sight of the wires is objectionable, covered with a light ornamental
wood casing. When the wires have been laid and the position of the
"pushes," etc., decided upon, the _blocks_ to which these are to be
fastened must be bedded in the plaster. These blocks may be either
square or circular pieces of elm, about 3 inches across, and 1 inch
thick, bevelled off smaller above, so as to be easily and firmly set in
the plaster. They may be fastened to the brickwork by two or three
brads, at such a height to lie level with the finished plaster. There
must of course be a hole in the centre of the block, through which the
wires can pass to the push. When the block has been fixed in place, the
zinc tube, if it does not come quite up to the block, should have its
orifice stopped with a little paper, to prevent any plaster, etc.,
getting into the tube. A little care in setting the block will avoid the
necessity of this makeshift. A long nail or screw driven into the block
will serve to mark its place, and save time in hunting for it after the
plastering has been done. When the blocks have been put in their places,
and the plastering, papering, etc., done, the wires are drawn through
the bottom hole of the push (after the lid or cover has been taken off),
Fig. 74, and a very small piece of the covering of the wire having been
removed from each wire, and brightened by sand papering, one piece is
passed round the shank of the screw connected with the lower spring,
shown to the _right_ in Fig. 74, and the other round the shank of the
screw connected to the upper spring, shown to the _left_ in the Fig. The
screws must be loosened to enable the operator to pass the wire under
their heads. The screws must then be tightened up to clench the wire
quite firmly. In doing this, we must guard against three things.
Firstly, in pulling the wire through the block, not to pull so tightly
as to cut the covering against the edge of the zinc tube. Secondly, not
to uncover too much of the wire, so as to make contact between the wires
themselves either at the back of the push, or at any other part of the
push itself. Thirdly, to secure good contact under the screws, by having
the ends of the wires quite clean, and tightly screwed down.
[Illustration: Fig. 74.]
[S] 69. In all cases where the wires have to be taken out of doors, such
as is necessitated by communication from house to outhouses, stables,
greenhouses, etc., over head lines (No. 18 gauge, gutta-percha tape and
tar covering) should be used. Where overhead lines are not admissible,
either as being eyesores, or otherwise, the wires may be laid in square
wooden casings of this section [box open up], the open part of
which must be covered by a strip of wood laid over it. The wood must
have been previously creosoted, in the same manner as railway sleepers.
This mode admits of easy examination. Iron pipes must, however, be used
if the lines have to pass under roads, etc., where there is any heavy
traffic. And it must be borne in mind that however carefully the iron
pipes, etc., be cemented at the joints, to make them watertight, there
will always be more electrical leakage in underground lines than in
overhead ones. In certain rare cases it may be needful to use _iron_
wires for this purpose instead of copper; in this case, as iron is six
or seven times a worse conductor than copper, a much heavier wire must
be employed to get the same effect. In other words, where iron wire is
used, its section must be not less than seven times that of the copper
wire which it replaces.
[S] 70. It is always preferable, where great distance (and, consequently,
greater expense) do not preclude it, to use wire for the leading as well
as for the returning circuit. Still, where for any reason this is not
practicable, it is perfectly admissible and possible to make a good
return circuit through the _earth_, that is to make the damp soil carry
the return current (see [S] 37). As recommended at the section just
quoted, this earth circuit must have at each extremity a mass of some
good conductor plunged into the moist ground. In _towns_, where there
are plenty of water mains and gas mains, this is a matter of no
difficulty, the only point being to ensure _good_ contact with these
masses of metal. In other places a hole must be dug into the ground
until the point of constant moisture is reached; in this must be placed
a sheet of lead or copper, not less than five square feet surface, to
which the _earth_ wires are soldered, the hole then filled in with
ordinary coke, well rammed down to within about six inches of the
surface, and then covered up with soil well trodden down. In making
contact with water or gas pipes, care must be taken to see that these
are _main_ pipes, so that they _do_ lead to earth, and not to a cistern
or meter only, as, if there are any white or red lead joints the circuit
will be defective. To secure a good contact with an iron pipe, bare it,
file its surface clean, rub it over with a bit of blue stone (sulphate
of copper) dipped in water; wipe it quite dry, bind it tightly and
evenly round with some bare copper wire (also well cleaned), No. 16
gauge. Bring the two ends of the wire together, and twist them up
tightly for a length of three or four inches. Now heat a large soldering
bit, put some resin on the copper wire, and solder the wire, binding
firmly down to the iron pipe. Do likewise to the projecting twist of
wire, and to this twist solder the end of the _return_ wire. On no
account should the two opposite _earth_ wires be soldered to water mains
and gas mains at the same time, since it has been found that the
different conditions in which these pipes find themselves is sufficient
to set up a current which might seriously interfere with the working of
the battery proper. Sometimes there is no means of getting a good
_earth_ except through the gas main: in this case we must be careful to
get to the street side of the meter, for the red lead joints will
prevent good conductivity being obtained. In out of the way country
places, if it is possible to get at the metal pipe leading to the well
of a pump, a very good "earth" can be obtained by soldering the wires to
that pipe, in the same manner as directed in the case of the water main.
The operator should in no case be contented with a merely twisted joint,
for the mere contact of the two metals (copper and iron) sets up in the
moist earth or air a little electric circuit of its own, and this
speedily rusts through and destroys the wires. The following
suggestions, by Messrs. Gent, on the subject of wiring, are so good,
that we feel that we shall be doing real service to the reader to quote
them here in full:--
"1st.--The description of wire to be used. It is of the utmost
importance that all wires used for electric bell purposes be of pure
copper and thoroughly well insulated. The materials mostly employed for
insulating purposes are indiarubber, gutta-percha, or cotton saturated
with paraffin. For ordinary indoor work, in dry places, and for
connecting doors and windows with burglar alarms, or for signalling in
case of fire, indiarubber and cotton covered wires answer well; but for
connecting long distances, part or all underground, or along walls, or
in damp cellars or buildings, gutta-percha covered wire is required, but
it should be fixed where it will not be exposed to heat or the sun, or
in very dry places, as the covering so exposed will perish, crack, and
in time fall off. This may be, to some extent, prevented by its being
covered with cotton; but we recommend for warm or exposed positions a
specially-prepared wire, in which rubber and compound form the
insulating materials, the outside being braided or taped.
"For ordinary house work, we refer to lay a wire of No. 18 or 20 copper,
covered to No. 14 or 11 with gutta-percha, and an outer covering of
cotton, which we called the 'battery' wire, this being the wire which
conveys the current from the battery to every push, etc., no matter how
many or in what position. The reason for selecting this kind is, that
with the gutta-percha wires the joints may be more perfectly covered and
made secure against damp. This is of the utmost importance in the case
of '_battery wires_,' as the current is always present and ready to
take advantage of any defect in the insulation to escape to an adjoining
wire, or to '_earth_,' and so cause a continuous waste of current. The
wires leading from the pushes to the signalling apparatus or bell we
call the 'line' wires. In these, and the rest of the house wires, the
perfect covering of the joints is important. For _line wires_ we usually
prefer No. 18 or 20 copper, covered with indiarubber, and an outer
coating of cotton, well varnished. In joining the '_battery wires_,' the
place where the junction is to be made must be carefully uncovered for
the distance of about an inch; the ends of the wire to be joined, well
cleaned, and tightly twisted together; with the flame of a spirit lamp
or candle the joint must be then heated sufficiently to melt fine solder
in strips when held upon it, having first put a little powdered resin on
the joint as a flux; the solder should be seen to run well and adhere
firmly to the copper wire. A piece of gutta-percha should then be taken
and placed upon the joint while warm, and with the aid of the spirit
lamp and wet fingers, moulded round until a firm and perfect covering
has been formed. _On no account use spirits_ in soldering. With the
_line wire_, it is best, as far as possible, to convey it all the way
from the push to the signal box or bell in _one continuous_ length. Of
course, when two or more pushes are required to the same wire, a
junction is unavoidable. The same process of joining and covering, as
given for the battery wire, applies to the line wire. Where many wires
are to be brought down to one position, a large tube may be buried in
the wall, or a wood casing fixed flush with the plaster, with a
removable front. The latter plan is easiest for fixing and for making
alterations and additions. For stapling the wires, in no case should the
wires be left naked. When they pass along a damp wall, it is best to fix
a board and _loosely_ staple them. _In no case allow more than one wire
to lie under the same staple_, and do not let the staples touch one
another. In many cases, electric bells have been an incessant annoyance
and complete failure, through driving the staples _tight up to the
wires_, and several wires to the same staple,--this must not be done on
any account. A number of wires may be twisted into a cable, and run
through a short piece of gutta-percha tube, and fastened with ordinary
gas hooks where it is an advantage to do so. In running the wires, avoid
hot water pipes, and do not take them along the same way as plumber
pipes. Underground wires must be laid between pieces of wood, or in a
gas or drain pipe, and not exposed in the bare earth without protection,
as sharp pieces of stone are apt to penetrate the covering and cause a
loss; in fact, in this, as in every part of fixing wires, the best wire
and the best protection is by far the cheapest in the end. The copper
wire in this case should not be less than No. 16 B.W.G., covered with
gutta-percha, to No. 9 or 10 B.W.G., and preferably an outer covering of
tape or braid well tarred. Outside wire, when run along walls and
exposed to the weather, should be covered with rubber and compound, and
varnished or tarred on an outer covering of tape or braid. Hooks or
staples must be well galvanised to prevent rusting, and fixed loosely.
If the wire is contained within an iron pipe, a lighter insulation may
be used: _but the pipe must be watertight_. In a new building, wires
must be contained within zinc or copper bell tubes. A 3/8 inch tube will
hold two wires comfortably. The tubes should be fixed to terminate in
the same positions in the rooms as ordinary crank bell levers,--that is,
about three feet from the floor. At the side of the fireplace a block of
wood should be fixed in the wall before any plaster is put on, and the
end of the tube should terminate in the centre of the same. A large nail
or screw may be put in to mark the place, so that the end of the tube
may be found easily when the plastering is finished. Bend the tube
slightly forward at the end, and insert a short peg of wood to prevent
dirt getting into the tube. Do the same at the side of, or over the bed
in bedroom. If the tubes are kept clean, the wires may be easily drawn
up or down as the case may require. The best way is to get a length of
ordinary copper bell wire, No. 16, sufficient to pass through the tube,
and having stretched it, pass it through and out at the other end. Here
have your coils of insulated wire, viz., one battery wire, which is
branched off to every push, and one line wire, which has to go direct to
the indicator or bells, and having removed a short portion of the
insulation from the end of each, they are tied to the bare copper wire
and drawn through. This is repeated wherever a push is to be fixed
throughout the building. In making connection with binding screws or
metal of any kind, it is of the utmost importance that everything should
be _perfectly clean_. _Joints_ in wire, whether tinned or untinned,
_must be soldered and covered_. We cannot impress this too earnestly on
fixers. Never bury wires in plaster unprotected, and in houses in course
of erection, the _tubes_ only should be fixed until the plastering is
finished, the wires to be run in at the same time that the other work is
completed."
[Illustration: Fig. 75.]
[S] 71. The wires having been laid by any of the methods indicated in the
preceding five sections, the fixer is now in a position to _connect up_.
No two houses or offices will admit of this being done in _exactly_ the
same way; but in the following sections most of the possible cases are
described and illustrated, and the intelligent fixer will find no
difficulty, when he has once grasped the principle, in making those
trifling modifications which the particular requirements may render
necessary. The first and simplest form, which engages our attention, is
that of a _single bell, battery, and push_, connected by wire only. This
is illustrated at Fig. 75. Here we see that the bell is connected by
means of one of the wires to the zinc pole of the battery, the push or
other contact being connected to the carbon pole of the same battery. A
second wire unites the other screw of the push or contact with the
second binding screw of the bell. There is no complete circuit until the
push is pressed, when the current circulates from the carbon or positive
pole of the battery, through the contact springs of the push, along the
wire to the bell, and then back again through the under wire to the zinc
or negative pole of the battery.[15] It must be clearly understood that
the exact position of battery, bell, and push is quite immaterial. What
is essential is, that the relative connections between battery, bell,
and push be maintained unaltered. Fig. 76 shows the next simplest case,
viz., that in which a single bell and push are worked by a single cell
through an "earth" return (see [S] 70). Here the current is made to pass
from the carbon pole of the battery to the push, thence along the line
wire to the bell. After passing through the bell, it goes to the
right-hand earth-plate E, passing through the soil till it reaches the
left-hand earth-plate E, thence back to the zinc pole of the battery. It
is of no consequence to the working of the bell whether the battery be
placed between the push and the left-hand earth-plate, or between the
bell and the right-hand earth-plate; indeed, some operators prefer to
keep the battery as near to the bell as possible. At Fig. 77 is shown
the mode by which a single battery and single bell can be made to ring
from two (or more) pushes situated in different rooms. Here it is
evident that, whichever of the two pushes be pressed, the current finds
its way to the bell by the upper wire, and back home again through the
lower wire; and, even if both pushes are down at once, the bell rings
just the same, for both pushes lead from the same pole of the battery
(the carbon) to the same wire (the line wire).
[Footnote 15: It must be borne in mind that the negative element is that
to which the positive pole is attached, and _vice vers[^a]_ (see ss. 8
and 9).]
[Illustration: Fig. 76.]
[Illustration: Fig. 77.]
In Fig. 78, we have a slight modification of the same arrangement, a
front-door _pull_ contact being inserted in the circuit; and here, in
view of the probably increased resistance of longer distance, _two_
cells are supposed to be employed instead of _one_, and these are
coupled up in series ([S] 40), in order to overcome this increased
resistance.
[Illustration: Fig. 78.]
The next case which may occur is where it is desired to ring two or more
bells from one push. There are two manners of doing this. The first mode
is to make the current divide itself between the two bells, which are
then said to be "_in parallel_." This mode is well illustrated both at
Figs. 79 and 80. As in these cases the current has to divide itself
among the bells, larger cells must be used, to provide for the larger
demand; or several cells may be coupled up in parallel ([S] 40). At Fig.
79 is shown the arrangement for two adjoining rooms; at Fig. 80, that to
be adopted when the rooms are at some distance apart. If, as shown at
Fig. 81, a switch similar to that figured in the cut Fig. 64 be inserted
at the point where the line wires converge to meet the push, it is
possible for the person using the push to ring both bells at once, or to
ring either the right-hand or the left-hand bell at will, according to
whether he turns the arm of the switch-lever on to the right-hand or
left-hand contact plate.
[Illustration: Fig. 79.]
[Illustration: Fig. 80.]
[Illustration: Fig. 81.]
The second mode of ringing two or more bells from one push is that of
connecting one bell to the other, the right-hand binding screw of the
one to the left-hand binding screw of the next, and so on, and then
connecting up the whole series of bells to the push and battery, as if
they were a single bell. This mode of disposing the bells is called the
_series_ arrangement. As we have already noticed at [S] 63, owing to the
difference in the times at which the different contact springs of the
various bells make contact, this mode is not very satisfactory. If the
bells are single stroke bells, they work very well in series; but, to
get trembling bells to work in series, it is best to adopt the form of
bell recommended by Mr. F. C. Allsop. He says: "Perhaps the best plan is
to use the form of bell shown at Fig. 82, which, as will be seen from
the figure, governs its vibrations, not by breaking the circuit, but by
shunting its coils. On the current flowing round the electro-magnet, the
armature is attracted, and the spring makes contact with the lower
screw. There now exists a path of practically no resistance from end to
end. The current is therefore diverted from the magnet coils, and passes
by the armature and lower screw to the next bell, the armature falling
back against the top screw, and repeating the previous operation so long
as the circuit is closed. Thus, no matter how many bells there be in the
series, the circuit is never broken. This form of bell, however, does
not ring so energetically as the ordinary form, with a corresponding
amount of battery power."
[Illustration: Fig. 82.]
[Illustration: Fig. 83.]
Fig. 83 illustrates the mode in which a bell, at a long distance, must
be coupled up to work with a local battery and relay. The relay is not
shown separately, but is supposed to be enclosed in the bell case. Here,
on pressing the push at the external left-hand corner, the battery
current passes into the relay at the distant station, and out at the
right-hand earth-plate E returning to the left-hand earth-plate E. In
doing this, it throws in circuit (just as long as the push is held down)
the right-hand local battery, so that the bell rings by the current sent
by the local battery, the more delicate relay working by the current
sent from the distant battery.
[Illustration: Fig. 84.]
[Illustration: Fig. 85.]
At Fig. 84, we have illustrated the mode of connecting up a continuous
ringing bell, with a wire return. Of course, if the distance is great,
or a roadway, etc., intervene, an overhead line and an earth plate may
replace the lines shown therein, or both lines may be buried. It is
possible, by using a Morse key (Fig. 65) constructed so as to make
contact in one direction when _not_ pressed down, and in the other
_when_ pressed down, to signal from either end of a circuit, using only
one line wire and one return. The mode of connecting up for this purpose
is shown at Fig. 85. At each end we have a battery and bell, with a
double contact Morse key as shown, the Morse key at each end being
connected through the intervention of the line wire through the central
stud. The batteries and bells at each station are connected to earth
plates, as shown. Suppose now we depress the Morse key at the right-hand
station. Since by so doing, we lift the back end of the lever, we throw
our own bell out of circuit, but make contact between our battery and
the line wire. Therefore the current traverses the line wire, enters in
the left-hand Morse key, and, since this is not depressed, can, and
does, pass into the bell, which therefore rings, then descends to the
left-hand earth-plate, returning along the ground to the battery from
whence it started at the right-hand E. If, on the contrary, the
_left_-hand Morse key be depressed, while the right-hand key is not
being manipulated, the current traverses in the opposite direction, and
the right-hand bell rings. Instead of Morse keys, _double contact_
pushes (that is, pushes making contact in one direction when _not_
pressed, and in the opposite _when_ pressed) may advantageously be
employed. This latter arrangement is shown at Fig. 86.
[Illustration: Fig. 86.]
It is also possible, as shown at Fig. 87, to send signals from two
stations, using but one battery (which, if the distance is great, should
be of a proportionate number of cells), two bells, and two ordinary
pushes. Three wires, besides the earth-plate or return wire, are
required in this case. The whole of the wires, except the _return_, must
be carefully insulated. Suppose in this case we press the right-hand
button. The current flows from the battery along the lower wire through
this right-hand push and returns to the distant bell along the top wire,
down the left-hand dotted wire back to the battery, since it cannot
enter by the left-hand press, which, not being pushed, makes no contact.
The left-hand bell therefore rings. If, on the other hand, the left-hand
push be pressed, the current from the carbon of the battery passes
through the left-hand push, traverses the central line wire, passes into
the bell, rings it, and descends to the right-hand earth plate E,
traverses the earth circuit till it reaches the left-hand earth plate E,
whence it returns to the zinc pole of the battery by the lower dotted
line.
[Illustration: Fig. 87.]
Fig. 88 shows how the same result (signalling in both directions) may be
attained, using only two wires, with earth return, and two Morse keys.
The direction of the current is shown by the arrows. Both wires must be
insulated and either carried overhead or underground, buried in tubes.
Fig. 89 shows the proper mode of connecting the entire system of bells,
pushes, etc., running through a building. The dotted lines are the wires
starting from the two poles of the battery (which should consist of more
cells in proportion as there is more work to do), the plain lines being
the wires between the pushes and the bell and signalling box. In this
illustration a door-pull is shown to the extreme left. Pendulum
indicators are usually connected up as shown in this figure, except that
the bell is generally enclosed in the indicator case. The wire,
therefore, has to be carried from the left-hand screw of the indicator
case direct to the upper dotted line, which is the wire returning to the
zinc pole of the battery. N.B.--When the wires from the press-buttons
are connected with the binding-screw, of the top of or inside of the
indicator case, the insulating material of the wires, at the point where
connection is to be made, must be removed, and the wires _carefully
cleaned_ and _tightly clamped down_.
[Illustration: Fig. 88.]
[Illustration: Fig. 89.]
When it is desired to connect separate bells to ring in other parts of
the building, the quickest way is to take a branch wire out of the
nearest _battery wire_ (the wire coming from the carbon pole), and carry
it to the push or pull, from thence to the bell, and from the bell back
to the zinc of the battery.
[S] 72. We should advise the fixer always to draw out a little sketch of
the arrangement he intends to adopt in carrying out any plan, as any
means of saving useless lengths of wire, etc., will then easily be seen.
In doing this, instead of making full sketches of batteries, he may use
the conventional signs [battery] for each cell of the battery, the thick
stroke meaning the carbon, the thin one the zinc. Pushes may be
represented by (.), earth-plates by [E] and pulls, switches, &c., as
shown in the annexed cut, Fig. 90, which illustrates a mode of
connecting up a lodge with a house, continuous bells being used, in such
a way that the lodge bell can be made to ring from the lodge pull, the
house bell ringing or not, according to the way the switch (shown at top
left-hand corner) is set. As it is set in the engraving, only the lodge
bell rings.
[Illustration: Fig. 90.]
[S] 73. There are still two cases of electric bell and signal fitting, to
which attention must be directed. The first is in the case of _ships_.
Here all the connections can be made exactly as in a house, the only
exception to be made being that the indicators must not be of the
_pendulum_, or other easily displaced type; but either of the form shown
at Fig. 67 or 68, in which the electro-magnet has to lift a latch to
release the fall or drop, against a pretty stiff spring. Besides being
thus firmly locking, so as not to be affected by the ship's motion, all
the wood work should be soaked in melted paraffin wax, the iron work
japanned, and the brass work well lacquered, to protect all parts from
damp. The second case requiring notice is that of _lifts_. Every
well-appointed lift should be fitted with electric bells and
indicators. In the cab of the lift itself should be placed an electric
bell, with as many double contact pushes and indicators as there are
floors to be communicated with. At the top and at the bottom of the left
shaft, as near to the landing side as possible, must be set two stout
wooden blocks (oak, elm, or other non-perishable wood). From top to
bottom of the shaft must then be stretched, in the same manner as a
pianoforte is strung, on stout metal pins, with threading holes and
square heads, as many No. 12 or 14 bare copper wires as there are floors
or landings, and two more for the battery and return wire respectively.
Care must be taken that these wires are strung perfectly parallel, and
that they are stretched quite taut, but not strained, otherwise they
will surely break. To the top of the cab, and in connection in the usual
manner by wires with the bell and indicator (which, as in the case of
ships, must be of the locking type, lest the jolts of the cab disturb
their action) must be attached a number of spoonbill springs, which
press against the naked wires running down the shaft. The shape of these
springs (which should be of brass) at the part where they press against
the bare wires, is similar to that of the spoon break of a bicycle. Some
operators use rollers at the end of the spring instead of spoonbills,
but these latter _rub_ the wires and keep up good contact, while the
rollers slip over the wires and do not keep them clean. By means of
these springs, the current from the batteries, which are best placed
either at the top of the lift itself, or in one of the adjacent rooms
(never at the bottom of the shaft, owing to the damp which always reigns
there), can be taken off and directed where it is desired, precisely as
if the batteries were in the cab itself. It is usual (though not
obligatory) to use the two wires _furthest_ from the landing as the go
and return battery wires, and from these, through the other wires, all
desired communication with the landings can be effected. To obtain this
end, it will be necessary to furnish every landing with a double contact
push and bell, and each bell and push must be connected up to the shaft
wires in the following mode:--
A wire must be led from the _lower_ contact spring of the double contact
push, to the _main battery carbon wire_ in the shaft. A second wire is
led from the _upper contact stop_ of the double contact push to the
bell, and thence to the _main battery zinc wire_ on the shaft. Lastly, a
third wire is taken from the _upper contact spring_ of the push and
connected to that particular wire in the shaft which by means of the
spoonbill springs connects the particular push and indicator in the cab,
destined to correspond with it. It will be seen that with the exception
of using the rubbing spoonbill springs and return wires in the shaft,
this arrangement is similar to that illustrated at Fig. 87.
[Illustration: Fig. 91.]
A glance at Fig. 91 will render the whole system of wiring and
connecting up with lifts and landing, perfectly clear. In connecting the
branch lines to the main bare copper wires in the shaft, in order that
the spoonbill springs should not interfere with them, they (the ends of
the branch wires) must be bent at right angles, like a letter [L], and the
upright portion soldered neatly to the _back_ of the shaft wire. Any
solder which may flow over to the _front_ of the wire must be carefully
scraped off to prevent any bumps affecting the smooth working of the
contact springs. It will be evident on examination of Fig. 91, that if
any of the pushes on the landings be pressed, the circuit is completed
between the battery at the top, through the two battery wires to the
bell and one of the indicators to the cab, and, on the other hand, that
if a push be pressed in the cab, a corresponding bell on the landing
will be rung, precisely as in Fig. 87.
Some fitters employ a many-stranded cable to convey the current to and
from the battery to the cab and landing, instead of the system of
stretched wires herein recommended; but this practice cannot be
advocated, as the continual bending and unbending of this cable,
repeated so frequently every day, soon breaks the leading wires
contained in the cable.
[S] 74. In many cases where a "call" bell alone is required, the battery
may be entirely dispensed with, and a small dynamo ([S] 15) employed
instead. The entire apparatus is then known as the "magneto-bell," and
consists essentially of two parts, viz., the generator, Fig. 92, and the
bell, Fig. 93. The _generator_ or _inductor_ consists of an armature,
which by means of a projecting handle and train of wheels can be
revolved rapidly between the poles of a powerful magnet; the whole being
enclosed in a box. The current produced by the revolution of the
armature is led to the two binding screws at the top of the box. By
means of two wires, or one wire and an earth circuit, the current is led
to the receiver or bell case, Fig. 93. Here, there are usually two
bells, placed very near one another, and the armature attached to the
bell clapper is so arranged between the poles of the double-bell
magnets, that it strikes alternately the one and the other, so that a
clear ringing is kept up as long as the handle is being turned at the
generator.
[Illustration: Fig. 92.]
[Illustration: Fig. 93.]
[Illustration: Fig. 94.]
If a _combined_ generator and bell be fitted at each end of a line, it
becomes possible to communicate both ways; one terminal of each
instrument must be connected to the line, and the other terminal on each
to earth. A combined generator and bell is shown at Fig. 94. These
instruments are always ready for use, require no battery or
press-buttons. The generator, Fig. 92, will ring seven bells
simultaneously, if required, so powerful is the current set up; and by
using a switch any number of bells, placed in different positions, can
be rung, by carrying a separate wire from the switch to the bell.
[Illustration: Fig. 95.]
[S] 75. Our work would not be complete unless we pointed out the means
necessary to detect faults in our work. In order to localise faults, two
things are requisite: first, a means of knowing whether the battery
itself is working properly, that is to say, giving the due _amount_ of
current of the right _pressure_, or E.M.F.; secondly, a means of
detecting whether there is leakage, or loss of current, or break of
circuit in our lines. Fortunately, the means of ascertaining these data
can be all combined in one instrument, known as a linesman's
galvanometer or detector, of which we give an illustration at Fig. 95.
It will be remembered ([S] 10) that if a current be passed over or under a
poised magnetic needle, parallel to it, the needle is immediately
deflected out of the parallel line, and swings round to the right or
left of the current, according to the _direction_ of the current;
likewise that the needle is deflected farther from the original position
as the current becomes stronger. The deflections, however, are not
proportionate to the strength of the current, being fairly so up to
about 25 to 30 degrees of arc out of the original position, but being
very much less than proportionate to the current strength as the needle
gets farther from the line of current; so that a current of infinite
strength would be required to send the needle up to 90 deg. On this
principle the detector is constructed. It consists of a lozenge-shaped
magnetic needle, suspended vertically on a light spindle, carrying at
one end a pointer, which indicates on a card, or metal dial, the
deflection of the needle. Behind the dial is arranged a flat upright
coil of wire (or two coils in many cases) parallel to the needle, along
which the current to be tested can be sent. The needle lies between the
front and back of the flat coil. The whole is enclosed in a neat wooden
box, with glazed front to show the dial, and binding screws to connect
up to the enclosed coil or coils. If the coil surrounding the needle be
of a few turns of coarse wire, since it opposes little resistance to the
passage of the current, it will serve to detect the presence of large
_quantities_ of electricity (many amp[e']res) at a low pressure; this is
called a _quantity_ coil. If, on the other hand, the coil be one of fine
wire, in many convolutions, as it requires more _pressure_, or E.M.F.,
or "intensity" to force the current through the fine high-resistance
wire, the instrument becomes one fitted to measure the voltage or
_pressure_ of the current, and the coil is known as the "intensity." If
both coils are inserted in the case, so that either can be used at will,
the instrument is capable of measuring either the quantity of
electricity passing, or the pressure at which it is sent, and is then
known as a quantity and intensity detector. No two galvanometers give
exactly the same deflection for the same amount of current, or the same
pressure; the fitter will therefore do well to run out a little table
(which he will soon learn by heart) of the deflection _his_ instrument
gives with 1, 2, 3, 4, 5 and 6 Leclanch['e]'s _coupled in parallel_, when
connected with the quantity coil. He will find the smaller sizes give
less current than the larger ones. In testing the deflections given by
the intensity coil, he must remember to couple his cells _in series_, as
he will get no increase in _tension_ or _pressure_ by coupling up in
parallel. In either case the cells should be new, and freshly set up,
say, within 24 hours. As some of my readers may like to try their skill
at constructing such a detector, I transcribe the directions given in
"Amateur work" by Mr. Edwinson:--
[S] 76. "Such an instrument, suitable for detecting the currents in an
electric bell circuit, may be made up at the cost of a few shillings for
material, and by the exercise of a little constructive ability. We shall
need, first of all, a magnetised needle; this can be made out of a piece
of watch spring. Procure a piece of watch spring two inches long, soften
it by heating it to redness, and allowing it to cool gradually in a bed
of hot ashes; then file it up to the form of a long lozenge, drill a
small hole in the centre to receive the spindle or pivot, see that the
needle is quite straight, then harden it by heating it again to a bright
red and plunging it at once into cold water. It now has to be
magnetised. To do this, rub it on a permanent horse-shoe, or other
magnet, until it will attract an ordinary sewing needle strongly, or
wrap it up in several turns of insulated line wire, and send many jerky
charges of electricity from a strong battery through the wire. When it
has been well magnetised, mount it on a spindle of fine hard wire, and
secure it by a drop of solder. We will next turn our attention to the
case, bobbin, or chamber in which the needle has to work. This may be
made out of cardboard entirely, or the end pieces may be made of ivory
or ebonite, or it may be made out of thin sheet brass; for our purpose
we will choose cardboard. Procure a piece of stout cardboard 4-3/4
inches long by 2 inches wide, double it to the form of a T[:a]ndstickor
match-box, and pierce it in exactly opposite sides, and in the centre of
those sides with holes for the needle spindle. Now cut another piece of
stout, stiff cardboard 2-3/4 inches long by 3/4 inch wide, and cut a
slit with a sharp knife to exactly fit the ends of the case or body
already prepared. The spindle holes must now be bushed with short
lengths of hard brass or glass bugles, or tubing, made to allow the
spindle free movement, and these secured in position by a little melted
shellac, sealing-wax, or glue. The needle must now be placed in the
case, the long end of the spindle first, then the short end in its
bearing; then, whilst the case with the needle enclosed is held between
the finger and thumb of the left hand, we secure the joint with a little
glue or with melted sealing-wax. The end-pieces are now to be put on,
glued, or sealed in position, and set aside to get firm, whilst we turn
our attention to other parts. The case, 5 inches by 4 inches by 2 inches
in depth, may be improvised out of an old cigar-box, but is best made of
thin mahogany or teak, nicely polished on the outside, and fitted with a
cover sliding in a groove, or hinged to form the back of the instrument.
The binding screws should be of the pattern known as the telegraph
pattern, fitted with nuts, shown at Fig. 27. A small brass handle to be
fitted to the top of the instrument, will also be handy. A circular
piece of smooth cardboard 3-1/4 inches in diameter, with a graduated
arc, marked as shown in Fig. 95, will serve the purpose of a dial, and a
piece of thin brass, bent to the form of [box open down], will be
required as a needle guard. The face of the dial may be a circular piece
of glass, held in a brass ogee, or a hole the size of the dial may be
cut in a piece of thin wood; this, glazed on the inside with a square of
glass, may be made to form the front of the instrument over the dial. An
indicating needle will also be required for an outside needle; this is
usually made of watch spring, and nicely blued; but it may be made of
brass or any other metal, one made of aluminium being probably the best
on account of its lightness. It must be pierced with a hole exactly in
the centre, so as to balance it as the beam of scales should be
balanced, and should one end be heavier than the other it must be filed
until they are equal.
We will now turn our attention to the coil.
Procure sixpennyworth of No. 36 silk-covered copper wire and wind three
layers of it very evenly on the coil case or bobbin, being careful in
passing the needle spindle not to pinch it or throw it out of truth.
When this has been wound on, it will be found that one end of the wire
points to the left and the other end to the right. These are destined to
be connected to the under side of the binding screws shown on the top of
Fig. 95. We therefore secure them to their respective sides with a touch
of sealing wax, and leave enough wire free at the ends to reach the
binding screws--say, about 6 inches. It is handy to have an additional
coil for testing strong currents, and as this may be combined in one
instrument at a trifle additional cost, we will get some line wire (No.
22) and wind six or eight turns of it around the coil outside the other
wire; one end of this wire will be attached to an additional binding
screw placed between the others, and the other end to left binding screw
shown. The coil thus prepared may now be mounted in position. Pierce the
board dial and the wood at its back with a hole large enough for the
needle spindle to pass through from the back to the centre of the dial.
See that the thick end of the inside needle hangs downwards, then place
the coil in the position it is intended to occupy, and note how far the
needle spindle protrudes on the face of the dial. If this is too long,
nip off the end and file it up taper and smooth until it will work
freely in a hole in the needle guard, with all parts in their proper
places. This being satisfactory, secure the coil in its place by sealing
wax, or, better still, by two thin straps of brass, held by screws at
each end, placed across the coil. Now clean the free ends of the coil
wires, insert them under the nuts of the binding screws, fix the
indicating needle on the end of the spindle outside, and see that it
hangs in a vertical position with the inside needle when the instrument
is standing on a level surface. Secure it in this position, screw on the
needle guard, fasten on the glass face, and the instrument will be
complete.
[S] 77. Provided thus with an efficient detector, the fitter may proceed
to test his work. In cases of _new installations_, take the wire off
the carbon binding screw of the battery and attach it to one screw of
the galvanometer (on the intensity coil side), next attach a piece of
wire from the other binding screw of the galvanometer (the central one)
so as to place the galvanometer in circuit. _There should be no movement
of the needle_, and in proportion to the deflection of the needle, so
will the loss or waste be. If loss is going on, every means must be used
to remedy it. It is of the utmost importance to the effective working of
the battery and bells that not the _slightest leakage_ or _local action_
should be allowed to remain. However slight such loss may be, it will
eventually ruin the battery. Let damp places be sought out, and the
wires removed from near them. Bad or injured coverings must also be
looked for, such as may have been caused by roughly drawing the wires
across angular walls, treading on them, or driving staples too tightly
over them. Two or more staples may be touching, or two or more wires
carelessly allowed to lie under one staple. The wire may have been bared
in some places in passing over the sharp edges of the zinc tube. The
backs of the pushes should be examined to see if too much wire has been
bared, and is touching another wire at the back of the push-case itself.
Or the same thing may be taking place at the junction with the relays or
at the indicator cases. Should the defect not be at any of these places,
the indicator should next be examined, and wire by wire detached (not
cut) until the particular wire in which the loss is going on has been
found. This wire should then be traced until the defect has been
discovered. In testing underground wires for a loss or break, it will be
necessary first to uncouple the _distant_ end, then to disconnect the
other end from the instruments, and attach the wire going underground to
the screw of the galvanometer. A piece of wire must then be taken from
the other screw of the detector to the carbon end of the battery, and a
second wire from the zinc end of the battery to the earth plate or other
connection. Proceeding to that part of the wire where the injury is
suspected, the wire is taken up, and a temporary earth connection having
been made (water main, gas pipe, etc.), and by means of a sharp knife
connected with this latter, the covering of the suspected wire
penetrated through to the wire, so as to make a good connection between
this suspected wire and the temporary earth plates. If, when this is
done, the needle is deflected fully, the injury is farther away from the
testing end, and other trials must be made farther on, until the spot is
discovered. Wherever the covering of the wire has been pierced for
testing, it must be carefully recovered, finished off with Prout's
elastic glue, or gutta-percha, and made quite sound. The connections
with the earth plates very frequently give trouble, the wires corrode or
become detached from the iron pipes etc., and then the circuit is
broken.
[S] 78. When the fitter is called to localise defects which may have
occurred in an installation which has been put up some time, before
proceeding to work let him ask questions as to what kind of defect there
is, and when and where it evinces itself. If all the bells have broken
down, and will not ring, either the battery or the main go and return
wires are at fault. Let him proceed to the battery, examine the binding
screws and connected wires for corrosion. If they are all right, let the
batteries themselves be tested to see if they are giving the right
amount of current. This should be done with the quantity coil of the
detector. Should the battery be faulty, it will be well to renew the
zincs and recharge the battery, if the porous cell be still in good
condition; if not, new cells should be substituted for the old ones.
Should the battery be all right, and still none of the bells ring, a
break or bad contact, or short circuit in the main wires near the
battery may be the cause of the mischief. If some bell rings
continuously, there must be a short circuit in the push or pushes
somewhere; the upper spring of one of the pushes may have got bent, or
have otherwise caught in the lower spring. _Pulls_ are very subject to
this defect. By violent manipulations on the part of mischievous butcher
or baker boys, the return spring may be broken, or so far weakened as
not to return the pull into the "off" position. If, the batteries being
in good order, any bell rings feebly, there is either leakage along its
line, or else bad contact in the push or in the connections of the wires
to and from the push. There should be platinum contacts at the ends of
the push springs; if there are not, the springs may have worked dirty at
the points of contact, hence the poor current and poor ringing. It is
seldom that the bells themselves, unless, indeed, of the lowest
quality, give any serious trouble. Still the set screw may have shaken
loose (which must then be adjusted and tightened up), or the platinum
speck has got solder on its face and therefore got oxidised. This may be
scraped carefully with a penknife until bright. Or, purposely or
inadvertently, no platinum is on the speck at all, only the solder. A
piece of platinum foil should be soldered on the spot, if this is so. Or
again (and this only in very bad bells), the electro-magnets being of
hard iron, may have retained a certain amount of _permanent magnetism_,
and pull the armature into permanent contact with itself. This can be
remedied by sticking a thin piece of paper (stamp paper will do) over
the poles of the magnet, between them and the armature. In no case
should the fitter _cut_ or _draw up_ out of tubes, etc., any wire or
wires, without having first ascertained that the fault is in that wire;
for, however carefully joints are made, it is rare that the jointed
places are so thoroughly insulated as they were before the cutting and
subsequent joining were undertaken. To avoid as much as possible cutting
uselessly, let every binding screw be examined and tightened up, and
every length of wire, which it is possible to get at, be tested for
continuity before any "slashing" at the wires, or furious onslaughts on
the indicator be consummated.
In conclusion, I beg to record my thanks for the very generous
assistance which I have received in the compilation of the foregoing
pages from the electrical firms of Messrs. Blakey Emmot, Binswanger,
Gent, Judson, Jensen, and Thorpe.
ADDENDUM.
THE GASSNER BATTERY.
Since the compilation of the foregoing pages, a _dry battery_, known by
the above name, has found great favour with electric-bell fitters. Its
peculiarity consists in the zinc element forming the outside cell. In
this is placed the carbon, which is separated from the zinc by a thick
paste or jelly made of gypsum and oxide of zinc. The cell can be placed
in any position, works as well on its side as upright, is not subject to
creeping, has an E.M.F. of about 1.5 volt, with an internal resistance
of only 0.25 ohm in the round form, and 0.6 in the flat form. The
Gassner dry battery polarizes much less quickly than the ordinary
Leclanch['e]. The only defects at present noticeable, are the flimsy
connections, and the fact that the outer cases being _metal_ must be
carefully guarded from touching one another. This can be effected by
enclosing in a partitioned _wooden box_.
INDEX.
A.
Acid, Chromic, 33, 46
---- Hydrobromic, 20
---- Hydrochloric, 20
---- Hydriodic, 20
---- Nitric, 20
---- Sulphuric, 20
Action in Bichromate, 47
---- Dotting, 116
---- of electric bell, 81
---- Leclanch['e], 35
---- Relay, 134
---- Rubbing, 116
---- of zinc on acids, 21
Agglomerate block, 38
---- Cell, 38
---- Compo, 38
Alarms, Burglar, 113
---- Fire, 123
---- Frost, 121
---- Thermometer, 122
---- Thief, 113
---- Watch, 124
Amber, 1
Amp[e']re, 55
Amp[e']re's law, 11
Annealing iron, 13
Arrangement of bells for lifts, 171
---- Ships, 170
Attraction, 3
B.
Batteries, 18
Battery agglomerate, 39
Battery, Bichromate, 48
---- Bunsen, 33
---- Chromic acid, 46
---- Daniell's, 29
---- Gassner (addendum), 186
---- Gent's, 44
---- Gravity, 31
---- Modified, 120
---- Grenet, 46
---- Grove, 33
---- Judson's, 41
---- Leclanch['e], 33
---- Reversed, 46
---- Minotto, 31
---- Smee's, 27
---- Walker's, 27
Bell action, case for, 88
Blocks, wooden, 150
Bobbins, electric bell, 67
Box for batteries, 43
Brushes, dynamo, 17
C.
Cable, many stranded, 174
Case for bell action, 88
Cells in parallel, 57
---- series, 53
Charging fluid, recipes, 48
---- Fuller, 49
Circuits, closed, 52, 118
---- Of bells complete in house, 168
---- For signalling, 167
---- In both directions, 168
Circuits of bells with Morse key, 165
In parallel, 161
Series, 162
With relay, 164
Single bell and wire, 159
Earth, 160
Two pushes, 161
Push and pull, 161
Open, 52
Closed circuit system, 118
Code for signalling, 130
Coil spring, 108
Conductors, 3
Connecting up, 144, 159
Contacts, burglar alarm, 113
Door, 116
Drawer, 121
Floor, 113
For closed circuits, 121
Mackenzie's humming, 113
Shop door, 116
Till, 121
Watch alarm, 124
Window sash, 116
Corrugated carbons, 41
Creeping in cells, 43
To remedy, 44
Callow's attachment, 99
Current, 54
To ring bell, 145
D.
Daniell's cell, 29
Action in, 29
Deflection of needle, 9, 11
Detector or galvanometer, to make, 178
Detent lever, 94
Door contact, 116
Dotting action, 116
Drawing out plans, 169
Dynamo, 15
Armature, 16
Brushes, 17
Commutator, 17
Dynamo, Cumulative effects, 17
Field magnets, 16
E.
Earth, 52
Plate, 53
Return, 153
Electric bell, action of, 81
Armature, 74
Base, 61
Bobbins, 67
Contact screw, 75
Continuous, 92
Circular bell, 106
Gong, 77
How to make, 60
In lifts, 171
Ships, 170
Jensen's, 101
Joining E. M. wire, 73
Magnets, 63
Magneto, 174
Mining, 106
Paraffining, 69
Platinum tip, 76
Putting together, 78
Single stroke, 91
Spring, 74
Thorpe's, 100
Trembling, 81, 90
Winding wire on, 71
Wire for, 69
Trumpet, 107
Electricity, sources of, 2
Electrodes, 26
Electro-motive force, 51
Electron, 1
E.M.F., 51
Excitation, 6
F.
Faults to detect, 182
Fire alarms, 123
Floor contacts, 113
Frost alarms, 121
Fuller charging, 49
G.
Galvanometer, 176
Gas evolved, 18
Gassner battery (addendum), 186
Generator (magneto), 174
Gent's battery, 44
Glue, Prout's elastic, 148
Graphite, 27
Gravity battery, 31
Daniell battery, 31
Modified, 120
Grenet battery, 46
Grove battery, 33
Gutta-percha, 148
I.
Indicator, 135
Automatic, 138
Drop, 136
Electric replacement, 136
Gent's, 140
Tripolar, 143
Mechanical replacement, 136
Mode of coupling up, 142
Pendulum, 139
Polarised, 139
Self replacing, 136
Semaphore, 136
Inductor, 174
Insulation, 68
Insulators, 4
Internal resistance, 56
Interior of push, 151
Iron, importance of soft, 65
Yoke, 66
J.
Jensen's bell, 101
Joining wires to push, 151
Judson's cell, 41
K.
Key, Morse, 129
L.
Leakage, 52
Leclanch['e] cell, 33
reversed, 46
Legge's contact, 115
Lever switches, 128
Lifts, bells for, 171
Localising faults, 144, 175
Lodge bell, 169
M.
Magnetic field, 14
Magneto bells, 175
Electric machines, 14, 15
Magnets, 13
Magnets producing electricity, 14
Magnetisation of iron, 12
Steel, 13
Manganese oxide, 33
Minotto cell, 31
Modified gravity battery, 120
Morse key, 129
Musical instrument, novel, 108
N.
Negative electricity, 7
Non-conductors, 3
Novel musical instrument, 108
O.
Ohm, 55
Ohm's law, 55
Open circuit, 52
Overhead lines, 152
P.
Paraffin, 69, 170
Percha, gutta, 148
Plans, drawing out, 169
Platinum, riveting, 76
Platinum, use of, 76
Plug switches, 128
Polarisation, 26
Positive electricity, 7
Proportions of bell parts, table of, 89
Pressels, 111
Prout's elastic glue, 148
Pulls, 111
Push, 92, 151, 109
Interior of, 151
Joining wires to, 151
R.
Relay, 96, 133
Action of, 134
Repulsion, 3
Resinous electricity, 7
Resistance of wire, table of, 146
Return current, 153
Riveting platinum, 76
Rubbing action, 116
S.
Ships, bells for, 170
Shop door contact, 116
Signalling by bells, 130
Code, 130
Silver platinised, 27
Single cell, 9
Sizes of Leclanch['e]'s, 42
Smee's cell, 27
Spring coil, 108
Standard size of wires, 146
Switches, lever, 128
Plug, 128
T.
Table of batteries, E.M.F. and R., 58
Conductors and insulators, 4, 68
Metals in acid, 8
Table of Proportions of bell parts, 89
Wire resistance, etc., 146
Testing new work, 182
Old, 183
Thermometer alarms, 122
Thorpe's Ball, 100
U.
Use of platinum, 76
V.
Vitreous electricity, 7
Volt, 53
W.
Walker's cell, 27
Watchman's clock, 124
Water level indicator, 127
Washer, insulating, 77
Window sash contact, 116
Wiping contact, 102
Wire covering, 147
In iron pipes, 152
In wooden boxes, 152
Iron, 152
Joining, 148
To push, 151
Laying in tubes, 149
Leading, 147, 150
Overhead, 152
Resistance, table of, 146
Return, 147, 150
Soldering iron, 148
Tinned, 147
Underground, 152
Wiring, general instructions, 155
Up, 144
Z.
Zinc, amalgamated, 22
Blacking, 45
Consumption, 21
Commercial, 19
Pure, 19
WILLIAM RIDER AND SON, PRINTERS, LONDON.
* * * * *
_Small crown 8vo, cloth._ _With many Illustrations._
WHITTAKER'S LIBRARY OF ARTS, SCIENCES,
MANUFACTURES AND INDUSTRIES.
MANAGEMENT OF ACCUMULATORS AND PRIVATE ELECTRIC LIGHT INSTALLATIONS.
A Practical Handbook by Sir DAVID SALOMONS, Bart., M. A.
4th Edition, Revised and Enlarged, with 32 Illustrations. Cloth 3s.
"To say that this book is the best of its kind would be a poor
compliment, as it is practically the only work on accumulators that
has been written."--_Electrical Review._
ELECTRICAL INSTRUMENT-MAKING FOR AMATEURS. A Practical Handbook. By
S. R. BOTTONE, Author of "The Dynamo," &c. With 60 Illustrations.
Second Edition. Cloth 3s.
ELECTRIC BELLS. By S. R. BOTTONE. With numerous Illustrations.
IN PREPARATION.
THE PROTECTION OF BUILDINGS FROM LIGHTNING. A Treatise on the Theory
of Lightning Conductors from a Modern Point of View. Being the
substance of two lectures delivered before the Society of Arts in
March, 1888. By OLIVER J. LODGE, LL.D., D.Sc, F.R.S., Professor of
Physics in University College, Liverpool.
Published with various amplifications and additions, with the
approval of the Society of Arts.
ELECTRICAL INFLUENCE MACHINES: Containing a full account of their
historical development, their modern Forms, and their Practical
Construction. By J. GRAY, B.Sc.
ELECTRICAL ENGINEERING IN OUR WORKSHOPS. A Practical Handbook. By
SYDNEY F. WALKER.
[_Ready Shortly_
* * * * *
Transcriber's Note
Page 12: changed "guage" to "gauge" (... cotton-covered copper wire,
say No. 20 gauge ...)
Page 35: changed "change" to "charge" (... losing at the same time its
electrical charge ...)
Page 55: changed "guage" to "gauge" (... 1 foot of No. 41 gauge pure
copper wire ...)
Page 64: changed "exaet" to "exact" (... of the exact diameter of the
turned ends of the cores ...)
Page 73: moved comma "Rivetting, is" to "Rivetting is," (Rivetting, is
perhaps, the best mode ...)
Page 81: added hyphen (... along the short length of wire to the
right-hand binding-screw ...)
Page 83: changed "head" to "heads" (... the possible defects of
electric bells may be classed under four heads: ...)
Page 92: changed "its" to "it" (... until it rests against the stop or
studs.)
Page 102: changed "contract-breaker" to "contact-breaker" (When the
contact-breaker is used, ...)
Page 103: changed "instead" to "Instead" (Instead of the armature and
clapper ...)
Page 132: in the Morse code for "BRING THE", the code for "H" has been
corrected from two dots to four dots.
Page 136: changed "eletro-magnet" to "electro-magnet" (... if the
electro-magnet were energised ...)
Page 137: changed "idicator" to "indicator" (since the indicator falls
forwards)
Page 146: changed "arrangment" to "arrangement" (the size and
arrangement of the batteries and wires)
Page 146: added comma "nails," (... chance contact with nails,
staples, metal pipes or other wires ...)
Page 179: changed "carboard" to "cardboard" (... for our purpose we
will choose cardboard.)
Page 179: changed "Tanstickor" to "T[:a]ndstickor" (... double it to the
form of a T[:a]ndstickor match-box, ...)
Page 185: suspected typo (unchanged) "Emmot" should perhaps be
"Emmott" (... the electrical firms of Messrs. Blakey Emmot, ...)
Page 186: changed "Leclanch[e']" to "Leclanch['e]" (... polarizes much
less quickly than the ordinary Leclanch['e].)
Page 187: changed two instances of "Amp['e]re" to "Amp[e']re" in the
index (Amp[e']re, 55 / Amp[e']re's law, 11)
End of Project Gutenberg's Electric Bells and All About Them, by S. R. Bottone