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HOW TO INSTALL
Electric Bells, Annunciators,
and Alarms.
INCLUDING
_Batteries, Wires and Wiring, Circuits, Pushes, Bells,
Burglar Alarms, High and Low Water Alarms,
Fire Alarms, Thermostats, Annunciators,
and the Location and Remedying
of Troubles._
BY
NORMAN H. SCHNEIDER,
Author of “The Study of Electricity for Beginners,” “Care and
Handling of Electric Plants,” etc., etc.
SECOND EDITION, ENLARGED
NEW YORK
SPON & CHAMBERLAIN, 123 LIBERTY STREET
LONDON
E. & F. N. SPON, Limited, 57 HAYMARKET, S.W.
1913
[No. 4]
Copyright 1904
Copyright 1913
By SPON & CHAMBERLAIN
The Camelot Press, 16–18 Oak St., New York
PREFACE
Among all the applications of electricity to domestic or commercial
uses, few are as widespread as the electric bell. Practically every
building used for a dwelling, storage or manufacture requires an
electric bell, annunciator or alarm system.
This book was written to explain in practical language how an electric
bell system operates and how it is installed; its success shown by its
large sale has resulted in this new edition which brings the subject up
to date.
Many new diagrams of annunciator and burglar alarm systems have been
added, together with descriptions and illustrations of wiring elevators
for electric bells, wiring for door openers, the use of transformers
for furnishing suitable ringing current from electric light circuits;
and high voltage bells intended to be used on other than the customary
low voltage battery circuits.
The author expresses his acknowledgment to the Western Electric
Company for diagrams of door opener circuits in connection with their
interphone systems, to Edwards and Company of New York for diagrams of
fire alarms, burglar alarms and annunciators, and to the Westinghouse
Company for illustrations of bell-ringing transformers.
CONTENTS
INTRODUCTION
PAGE
Introduction. The principle of an electric bell. ix
CHAPTER I
The Leclanche cell--Polarization--Setting tip--The dry
cell--The gravity cell--Connecting up cells 1
CHAPTER II
The single stroke bell--The shunt bell--The differential
bell--The continuous ring bell--The waterproof bell--Forms
of gongs--The buzzer--Long distance bells--The relay--The
push--Three point or double contact push--Floor push--Door
pull--Indicating push 9
CHAPTER III
Bell wires--Joints--Running wires--How to put up a door
bell--Combinations of bells, pushes and batteries--Faults
in bells, faults in wiring--How to locate and remedy faults 23
CHAPTER IV
Fire alarms--Thermostats--Metallic thermostats--Mercury
thermostat--How to connect thermostats--Water level
indicators--Burglar alarms--Open and closed circuit
alarms--Window, door and shade springs--Alarm matting--Yale
lock alarm--Door trip alarm 40
CHAPTER V
The annunciator drop--The needle or arrow drop--The pendulum
drop--Wiring up annunciators--Return or fire call
systems--Double wire system--Western Electric single wire
system 55
CHAPTER VI
Three-wire return call system--Installing elevator
annunciators--Burglar alarm annunciators--Clock
alarm circuit--Bells for high voltages--Bell-ringing
transformers--Combination bell, door opener and telephone
circuits--Fire alarm circuit--Interior fire alarm
system--Fire alarm system for considerable areas 64
LIST OF ILLUSTRATIONS
FIG. PAGE
1 Electric bell, push, and battery x
2 Leclanche cell 1
3 Dry cell 4
4 Gravity cell 5
5 Vibrating bell 10
6 Single stroke bell 10
7 Shunt or short circuit bell 10
8 Continuous ring bell 13
9 Waterproof bell 14
10 Dome gong 15
11 Tea gong 15
12 Cow gong 15
13 Sleigh bell gong 15
14 Spiral gong 15
15 Relay and circuit 16
16 Door push 19
17 Pear push 19
18 Door push 19
19 Wall push 19
20 Floor push 20
21 Door pull attachment 22
22 Wire joint first operation 25
23 Wire joint second operation 25
24 Wire joint insulating 25
25 Section of house showing wiring 29
26 Bell with ground return 30
27 Pushes in multiple 31
28 Bells in series 31
29 Bells in multiple 31
30 Two bells and two pushes 32
31 Two bells and two pushes 32
32 Two bells, two pushes and one battery 33
33 Double contact push 33
34 Grounded bell 34
35 Tongue test of wiring 38
36 Knife test of wiring 38
37 Knife test of wiring 39
38 Metallic thermostat 40
39 Mercury thermostat 41
40 Mercury thermostat circuit 42
41 Water level alarm 44
42 Lever water level alarm 45
43 High or low water level alarm 45
44 Window spring for burglar alarm 47
45 Burglar alarm--closed circuit 47
46 Special bell connection for burglar alarm 48
47 Special bell connection for burglar alarm 49
48 Burglar alarm and relay 50
49 Window-shade contact spring 51
50 House wired for burglar alarm 52
51 Door trip alarm 53
52 Annunciator drop 55
53 Needle drop 56
54 Needle drop indicating 56
55 Pendulum drop 57
56 Annunciator drop circuit 58
57 Simple annunciator circuit 59
58 Annunciator and fire call circuit 60
59 Single-wire room and fire call 61
60 Three-wire return call circuit 65
61 Elevator bells and annunciator circuit 67
62 Burglar alarm annunciator circuit 69
63 Clock alarm circuit 71
64 Bell-ringing transformer 73
65 Bell-ringing transformer with three secondary voltages 73
66 Western Electric interphone system 75
67 Western Electric interphone system for more extensive
service 77
68 Fire alarm circuit 79
69 Interior fire alarm circuit 81
70 Fire alarm circuit for considerable areas 82
INTRODUCTION
An electric bell depends for its action on the fact that a piece of
iron wound with insulated wire becomes a magnet and will attract
another piece of iron just so long as an electric current is allowed to
travel through the wire.
The instant the current ceases, the magnetism also ceases, and the
attracted piece of iron (termed the armature) is no longer held in
contact.
The general construction of an electric bell is shown in Fig. 1. _M M_
are coils of insulated wire wound on soft iron cores. _A_ is a soft
iron armature mounted on a flat spring so that it is normally kept a
slight distance away from the soft iron cores. _S_ is a brass screw
with a platinum tip touching a platinum disc on a spring attached to
the armature.
When the push button _P_ is pressed down, its two brass springs touch
each other, the current from the battery cell _B_ then flows through
the wire _W_, through the push _P_, through the coils _M M_, along _A_
to the platinum disc, out at _S_, which touches this disc, and back to
the battery.
[Illustration: FIG. 1]
The instant this is done the current causes the iron cores to become
magnets, they attract _A_, which then breaks contact at _S_. The spring
mounting of _A_ causes it to jump back to its first position, _S_ then
touches the platinum disc again, the current flows as before, and the
armature is again attracted only to break contact with _S_ and fly back.
This continual making and breaking of the circuit keeps up as long as
the push is pressed, a ball mounted on _A_ by means of a rod strikes
against the gong _G_ causing a continuous ringing of the bell. The
wires leading between the bell, battery cell and push must all be
insulated, that is, covered with cotton, rubber, etc., which prevents
the leakage of current should two wires cross each other. Copper wire
is mostly used for circuits indoors, the details of the kind and size
of wire will be given later on.
The main parts of an electric bell circuit are then--the battery to
supply the electric current; the circuit, or wires, to carry this
current; a push, or circuit breaker, to control the current flow; and a
bell to utilize the current.
CHAPTER I
_The Battery_
=The Battery Cell.= The battery cell most used in electric bell work is
the Leclanche, or some modification of it.
[Illustration: FIG. 2]
The Leclanche battery cell is shown in Fig. 2, where _J_ is a glass
jar, _Z_ a rod of zinc, and _P_ a jar of porous earthenware containing
a carbon rod surrounded by powdered carbon and peroxide of manganese.
In setting up this cell about four ounces of sal ammoniac (chloride of
ammonia) are put into the jar and enough water added to come about half
way up the jar.
The porous jar _P_ and the zinc _Z_ are then inserted, and the cell is
ready for use in a few minutes after the liquid has soaked through the
earthenware into the carbon-manganese mixture. Water is often poured
into the porous jar through holes in its top to hasten this wetting.
Wires are clamped by nuts or set-screws to the negative terminal on the
zinc or the positive terminal on the carbon, it generally not being of
consequence which terminal is attached to either wire of the circuit.
A battery cell could be constructed without the manganese, using
simply a plate of carbon and a rod of zinc, but hydrogen gas would be
generated on the carbon plate when the cell was working and would stop
the current flowing.
This is called polarization, and peroxide of manganese is a
de-polarizer, because it combines with this hydrogen gas almost as fast
as it is generated, and prevents, to a great extent, the polarization.
But it does not stop it entirely, as will be seen if the Leclanche cell
is kept working above its capacity. Then the hydrogen is generated too
fast for the manganese to destroy it, and the cell ceases to work. In
this case a rest will often restore the cell to its former power.
Cells which have been almost unable to make a bell give even a single
tap have been found good again when allowed to remain at rest over
night.
In setting up a battery cell no liquid should be splashed on the brass
terminals or corrosion will take place. Every metal surface where
connection is made to allow electric current to pass _must_ be clean
and bright, and all screws, or nuts, holding wires must be screwed up
tight so that the wires are firmly clamped.
Loose or dirty connections are the cause of probably eight out of every
ten troubles affecting bells and batteries.
When the fluid in a Leclanche cell becomes milky, more sal ammoniac
must be added. Or, better still, throw out the old solution, wash the
porous jar thoroughly in clean water, scrape the zinc bright, and half
fill the cell with fresh solution.
The zinc wearing away rapidly or becoming covered with crystals, and a
strong smell of ammonia, show generally that the cell is being worked
too hard, or that the current is leaking where it should not.
A zinc rod in a cell working the average door bell should last for six
months, the porous jar for a year.
=The Dry Cell.= The Leclanche cell being a cell with much free liquid
is liable to dry up if not watched. The dry cell (Fig. 3) is a modern
form of the Leclanche where the liquid is held by an absorbent
material, such as blotting paper, or plaster.
[Illustration: FIG. 3]
A typical dry cell[A] is shown in the figure. An outside case of zinc
is lined with blotting paper dampened with chloride of zinc and sal
ammoniac. A carbon rod is then inserted in the centre and packed around
with carbon dust and peroxide of manganese. The latter mixture is also
somewhat dampened.
[A] For full description of this class of battery see No. 3
Book on “Dry Batteries.”
Molten wax, or a suitable composition, is then poured on top of the
contents of the cell to seal it up and prevent the evaporation of
the fluid. A terminal on the carbon rod and another on the zinc case
complete the cell.
[Illustration: FIG. 4]
The voltage of both the Leclanche and the dry cell is about 1.45, when
it goes below this it indicates that the cell is worked out.
The two cells described are known as open-circuit cells and are only
intended for intermittent working.
When a current is needed for a long period at a time a closed circuit
cell should be used, such as the gravity Daniell cell.
=The Gravity Daniell Cell.= The gravity cell, Fig. 4, has a zinc block
_Z_ suspended from the side of the jar and a number of copper leaves
_C_ standing on edge at the bottom. A quantity of bluestone (sulphate
of copper) is poured over the copper leaves and the jar filled with
water.
During the working of this cell, copper is deposited on the copper
plate, and sulphate of zinc formed at the zinc. To hasten the action
a small quantity of zinc sulphate can be added to the solution when
setting up the cell.
The name of this cell comes from the fact that the copper solution
being heavier remains at the bottom of the jar. If the cell is not
worked enough, all the solution will become blue and the zinc will
blacken. If very dirty from this cause, remove the zinc, scrape and
wash it thoroughly. Throw out all the solution, add new sulphate and
water and replacing the zinc, then put the cell on short circuit by
connecting the copper and zinc together for a few hours.
=E. M. F.= The e. m. f. of a gravity cell is within a fraction of one
volt, its current nearly one-half ampere.
Warmth makes it give a greater current; on no account let a gravity
cell freeze.
=Resistance of a Cell.= The fluids in a cell do not conduct electricity
as well as copper does; they offer more resistance and thus reduce the
current output.
The internal resistance of a cell may be lowered by using large zinc
plates curled around the porous pot.
The Samson cell has a large zinc plate bent in the form of a cylinder,
the carbon-manganese combination standing in the centre of it.
The dry cell also has a large zinc, the internal resistance being thus
much lowered, the current output is increased. This is by reason of
Ohm’s law, which teaches that to increase the current flow, either the
voltage of the battery must be increased, or the resistance decreased.
But increased current means lessened life; there is only just so much
energy in a cell mainly dependent on the quantity of chemicals.
=Grouping of Cells.= Cells may be grouped in a battery to get increased
voltage, or increased amperage. When connected for the former, they are
in series, the carbon of one is connected to the zinc of the next, and
so on.
If all the carbons are connected together and all the zincs, they are
in multiple, and will give the same voltage as of one cell but the
combined amperage of all.
In ordinary bell work the series is the general connection, the higher
the resistance of the circuit, or the longer the wires, the more
voltage is required.