TELEPHONE TRAIN DISPATCHING[A]
It has been only within the past three few that the telephone has begun
to replace the telegraph for handling train movements. The telegraph and
the railroads have grown up together in this country since 1850, and in
view of the excellent results that the telegraph has given in train
dispatching and of the close alliance that has always naturally existed
between the railway and the telegraph, it has been difficult for the
telephone, which came much later, to enter the field.
=Rapid Growth.= The telephone has been in general use among the
railroads for many years, but only on a few short lines has it been used
for dispatching trains. In these cases the ordinary magneto circuit and
instruments have been employed, differing in no respect from those used
in commercial service at the present time. Code ringing was used and the
number of stations on a circuit was limited by the same causes that
limit the telephones on commercial party lines at present.
The present type of telephone dispatching systems, however, differs
essentially from the systems used in commercial work, and is, in fact, a
highly specialized party-line system, arranged for selective ringing and
_many stations_. The first of the present type was installed by the New
York Central and Hudson River Railroad in October, 1907, between Albany
and Fonda, New York, a distance of 40 miles. This section of the road is
on the main line and has four tracks controlled by block signals.
The Chicago, Burlington, and Quincy Railroad was the second to install
train-dispatching circuits. In December, 1907, a portion of the main
line from Aurora to Mendota, Illinois, a distance of 46 miles, was
equipped. This was followed in quick succession by various other
circuits ranging, in general, in lengths over 100 miles. At the present
time there are over 20 train-dispatching circuits on the Chicago,
Burlington, and Quincy Railroad covering 125 miles of double track, 28
miles of multi-track, and 1,381 miles of single track, and connecting
with 286 stations.
Other railroads entered this field in quick order after the initial
installations, and at the present time nearly every large railroad
system in the United States is equipped with several telephone
train-dispatching circuits and all of these seem to be extending their
systems.
In 1910, several railroads, including the Delaware, Lackawanna, and
Western, had their total mileage equipped with telephone dispatching
circuits. The Atchison, Topeka, and Santa Fe Railroad is equipping its
whole system as rapidly as possible and already is the largest user of
this equipment in this country. From latest information, over 55
railroads have entered this field, with the result that the telephone is
now in use in railroad service on over 29,000 miles of line.
=Causes of Its Introduction.= The reasons leading to the introduction of
the telephone into the dispatching field were of this nature: First, and
most important, was the enactment of State and Federal Laws limiting to
nine hours the working day of railroad employes transmitting or
receiving orders pertaining to the movement of trains. The second, which
is directly dependent upon the first, was the inability of the railroads
to obtain the additional number of telegraph operators which were
required under the provisions of the new laws. It was estimated that
15,000 additional operators would be required to maintain service in the
same fashion after the new laws went into effect in 1907. The increased
annual expense occasioned by the employment of these additional
operators was roughly estimated at $10,000,000. A third reason is found
in the decreased efficiency of the average railway and commercial
telegraph operator. There is a very general complaint among the
railroads today regarding this particular point, and many of them
welcome the telephone, because, if for no other reason, it renders them
independent of the telegrapher. What has occasioned this decrease in
efficiency it is not easy to say, but there is a strong tendency to lay
it, in part, to the attitude of the telegraphers' organization toward
the student operator. It is a fact, too, that the limits which these
organizations have placed on student operators were directly
responsible for the lack of available men when they were needed.
=Advantages.= In making this radical change, railroad officials were
most cautious, and yet we know of no case where the introduction of the
telephone has been followed by its abandonment, the tendency having been
in all cases toward further installations and more equipment of the
modern type. The reasons for this are clear, for where the telephone is
used it does not require a highly specialized man as station operator
and consequently a much broader field is open to the railroads from
which to draw operators. This, we think, is the most far-reaching
advantage.
The telephone method also is faster. On an ordinary train-dispatching
circuit it now requires from 0.1 of a second to 5 seconds to call any
station. In case a plurality of calls is desired, the dispatcher calls
one station after another, getting the answer from one while the next is
being called, and so on. By speaking into a telephone many more words
may be transmitted in a given time than by Morse telegraphy. It is
possible to send fifty words a minute by Morse, but such speed is
exceptional. Less than half that is the rule. The gain in high speed,
therefore, which is obtained is obvious and it has been found that this
is a most important feature on busy divisions. It is true that in the
issuance of "orders," the speed, in telephonic train dispatching, is
limited to that required to write the words in longhand. But all
directions of a collateral character, the receipt of important
information, and the instantaneous descriptions of emergency situations
can be given and received at a speed limited only by that of human
speech.
The dispatcher is also brought into a closer personal relation with the
station men and trainmen, and this feature of direct personal
communication has been found to be of importance in bringing about a
higher degree of co-operation and better discipline in the service.
Telephone dispatching has features peculiar to itself which are
important in improving the class of service. One of these is the
"answer-back" automatically given to the dispatcher by the waystation
bell. This informs the dispatcher whether or not the bell at the station
rang, and excuses by the operators that it did not, are eliminated.
Anyone can answer a telephone call in an emergency. The station
operator is frequently agent also, and his duties often take him out of
hearing of the telegraph sounder. The selector bell used with the
telephone can be heard for a distance of several hundred feet. In
addition, it is quite likely that anyone in the neighborhood would
recognize that the station was wanted and either notify the operator or
answer the call.
In cases of emergency the train crews can get into direct communication
with the dispatcher immediately, by means of portable telephone sets
which are carried on the trains. It is a well-known fact that every
minute a main line is blocked by a wreck can be reckoned as great loss
to the railroad.
It is also possible to install siding telephone sets located either in
booths or on poles along the right-of-way. These are in general service
today at sidings, crossings, drawbridges, water tanks, and such places,
where it may be essential for a train crew to reach the nearest
waystation to give or receive information.
The advantage of these siding sets is coming more and more to be
realized. With the telegraph method of dispatching, a train is ordered
to pass another train at a certain siding, let us say. It reaches this
point, and to use a railroad expression, "goes into the hole." Now, if
anything happens to the second train whereby it is delayed, the first
train remains tied up at that siding without the possibility of either
reaching the dispatcher or being reached by him. With the telephone
station at the siding, which requires no operator, this is avoided. If a
train finds itself waiting too long, the conductor goes to the siding
telephone and talks to the dispatcher, possibly getting orders which
will advance him many miles that would otherwise have been lost.
It is no longer necessary for a waystation operator to call the
dispatcher. When one of these operators wishes to talk to the
dispatcher, he merely takes his telephone receiver off the hook, presses
a button, and speaks to the dispatcher.
With the telephone it is a simple matter to arrange for provision so
that the chief dispatcher, the superintendent, or any other official may
listen in at will upon a train circuit to observe the character of the
service. The fact that this can be done and that the operators know it
can be done has a very strong tendency to improve the discipline.
The dispatchers are so relieved, by the elimination of the strain of
continuous telegraphing, and can handle their work so much more quickly
with the telephone, that in many cases it has been found possible to
increase the length of their divisions from 30 to 50 per cent.
=Railroad Conditions.= One of the main reasons that delayed the
telephone for so many years in its entrance to the dispatching field is
that the conditions in this field are like nothing which has yet been
met with in commercial telephony. There was no system developed for
meeting them, although the elements were at hand. A railroad is divided
up into a number of divisions or dispatchers' districts of varying
lengths. These lengths are dependent on the density of the traffic over
the division. In some cases a dispatcher will handle not more than 25
miles of line. In other cases this district may be 300 miles long. Over
the length of one of these divisions the telephone circuit extends, and
this circuit may have upon it 5 or 50 stations, _all of which may be
required to listen upon the line at the same time_.
It will be seen from this that the telephone dispatching circuit
partakes somewhat of the nature of a long-distance commercial circuit in
its length, and it also resembles a rural line in that it has a large
number of telephones upon it. Regarding three other characteristics,
namely, that many of these stations may be required to be in on the
circuit simultaneously, that they must all be signaled selectively, and
that it must also be possible to talk and signal on the circuit
simultaneously, a telephone train-dispatching circuit resembles nothing
in the commercial field. These requirements are the ones which have
necessitated the development of special equipment.
=Transmitting Orders.= The method of giving orders is the same as that
followed with the telegraph, with one important exception. When the
dispatcher transmits a train order by telephone, he writes out the order
as he speaks it into his transmitter. In this way the speed at which the
order is given is regulated so that everyone receiving it can easily get
it all down, and a copy of the transmitted order is retained by the
dispatcher. All figures and proper names are spelled out. Then after an
order has been given, it is repeated to the dispatcher by each man
receiving it, and he underlines each word as it comes in. This is now
done so rapidly that a man can repeat an order more quickly than the
dispatcher can underline. The doubt as to the accuracy with which it is
possible to transmit information by telephone has been dispelled by this
method of procedure, and the safety of telephone dispatching has been
fully established.
=Apparatus.= The apparatus which is employed at waystations may be
divided into two groups--the selector equipment and the telephone
equipment. The selector is an electro-mechanical device for ringing a
bell at a waystation when the dispatcher operates a key corresponding to
that station. At first, as in telegraphy, the selector magnets were
connected in series in the line, but today all systems bridge the
selectors across the telephone circuit in the same way and for the same
reasons that it is done in bridging party-line work. There are at the
present time three types of selectors in general use, and the mileage
operated by means of these is probably considerably over 95 per cent of
the total mileage so operated in the country.
[Illustration: Fig. 475. Western Electric Selector]
[Illustration: Fig. 476. Western Electric Selector]
_The Western Electric Selector._ This selector is the latest and perhaps
the simplest. Fig. 475 shows it with its glass dust-proof cover on, and
Fig. 476 shows it with the cover removed. This selector is adapted for
operating at high speed, stations being called at the rate of ten per
second.
The operating mechanism, which is mounted on the front of the selector
so as to be readily accessible, works on the central-energy
principle--the battery for its operation, as well as for the operation
of the bell used in connection with it, both being located at the
dispatcher's office. The bell battery may, however, be placed at the
waystation if this is desired.
The selector consists of two electromagnets which are bridged in series
across the telephone circuit and are of very high impedance. It is
possible to place as many of these selectors as may be desired across a
circuit without seriously affecting the telephonic transmission.
Direct-current impulses sent out by the dispatcher operate these
magnets, one of which is slow and the other quick-acting. The first
impulse sent out is a long impulse and pulls up both armatures, thereby
causing the pawls above and below the small ratchet wheel, shown in Fig.
476, to engage with this wheel. The remaining impulses operate the
quick-acting magnet and step the wheel around the proper number of
teeth, but do not affect the slow-acting magnet which remains held up by
them. The pawl connected to the slow-acting magnet merely serves to
prevent the ratchet wheel from turning back. Attached to the ratchet
wheel is a contact whose position can be varied in relation to the
stationary contact on the left of the selector with which this engages.
This contact is set so that when the wheel has been rotated the desired
number of teeth, the two contacts will make and the bell be rung. Any
selector may thus be adjusted for any station, and the selectors are
thus interchangeable. When the current is removed from the line at the
dispatcher's office, the armatures fall back and everything is restored
to normal. An "answer-back" signal is provided with this selector
dependent upon the operation of the bell. When the selector at a station
operates, the bell normally rings for a few seconds. The dispatcher,
however, can hold this ring for any length of time desired.
The keys employed at the dispatcher's office for operating selectors are
shown in Fig. 477. There is one key for each waystation on the line and
the dispatcher calls any station by merely giving the corresponding key
a quarter turn to the right. Fig. 478 shows the mechanism of one of
these keys and the means employed for sending out current impulses over
the circuit. The key is adjustable and may be arranged for any station
desired by means of the movable cams shown on the rear in Fig. 478,
these cams, when occupying different positions, serving to cover
different numbers of the teeth of the impulse wheel which operate the
impulse contacts.
[Illustration: Fig. 477. Dispatcher's Keys]
[Illustration: Fig. 478. Dispatcher's Key Mechanism]
_The Gill Selector._ The second type of selector in extensive use
throughout the country today is known as the Gill, after its inventor.
It is manufactured for both local-battery and central-energy types, the
latter being the latest development of this selector. With the
local-battery type, the waystation bell rings until stopped by the
dispatcher. With the central-energy type it rings a definite length of
time and can be held for a longer period as is the case with the Western
Electric selector. The selector is operated by combinations of
direct-current impulses which are sent out over the line by keys in the
dispatcher's office.
[Illustration: Fig. 479. Gill Selector]
The dispatcher has a key cabinet, and calls in the same way as already
described, but these keys instead of sending a series of quick impulses,
send a succession of impulses with intervals between corresponding to
the particular arrangement of teeth in the corresponding waystation
selector wheel. Each key, therefore, belongs definitely with a certain
selector and can be used in connection with no other.
A concrete example may make this clearer. The dispatcher may operate key
No. 1421. This key starts a clockwork mechanism which impresses at
regular intervals, on the telephone line, direct-current impulses, with
intervals between as follows: 1-4-2-1. There is on the line one selector
corresponding to this combination and it alone, of all the selectors on
the circuit, will step its wheel clear around so that contact is made
and the bell is rung. In all the others, the pawls will have slipped out
at some point of the revolution and the wheels will have returned to
their normal positions.
The Gill selector is shown in Fig. 479. It contains a double-wound relay
which is bridged across the telephone circuit and operates the selector.
This relay has a resistance of 4,500 ohms and a high impedance, and
operates the selector mechanism which is a special modification of the
ratchet and pawl principle. The essential features of this selector are
the "step-up" selector wheel and a time wheel, normally held at the
bottom of an inclined track.
The operation of the selector magnet pushes the time wheel up the track
and allows it to roll down. If the magnet is operated rapidly, the wheel
does not get clear down before being pushed back again. A small pin on
the side of the pawl, engaging the selector wheel normally, opposes the
selector wheel teeth near their outer points. When the time wheel rolls
to the bottom of the track, however, the pawl is allowed to drop to the
bottom of the tooth. Some of the teeth on the selector wheel are formed
so that they will effectually engage with the pawl only when the latter
is in normal position, while others will engage only while the pawl is
at the bottom position; thus innumerable combinations can be made which
will respond to certain combinations of rapid impulses with intervals
between. The correct combination of impulses and intervals steps the
selector wheel clear around so that a contact is made. The selector
wheels at all other stations fail to reach their contact position
because at some point or points in their revolution the pawls have
slipped out, allowing the selector wheels to return "home."
The "answer-back" is provided in this selector by means of a few
inductive turns of the bell circuit which are wound on the selector
relay. The operation of the bell through these turns induces an
alternating current in the selector winding which flows out on the line
and is heard as a distinctive buzzing noise by the dispatcher.
[Illustration: Fig. 480. Cummings-Wray Dispatcher's Sender]
_The Cummings-Wray Selector._ Both of the selectors already described
are of a type known as the _individual-call_ selectors, meaning that
only one station at a time can be called. If a plurality of calls is
desired, the dispatcher calls one station after another. The third type
of selector in use today is of a type known as the _multiple-call_, in
which the dispatcher can call simultaneously as many stations as he
desires.
The Cummings-Wray selector and that of the Kellogg Switchboard and
Supply Company are of this type and operate on the principle of
synchronous clocks. When the dispatcher wishes to put through a call, he
throws the keys of all the stations that he desires and then operates a
starting key. The bells at all these stations are rung by one operation.
The dispatcher's sending equipment of the Cummings-Wray system is shown
in Fig. 480, and the waystation selector in Fig. 481. It is necessary
with this system for the clocks at all stations to be wound every eight
days.
[Illustration: Fig. 481. Cummings-Wray Selector]
In the dispatcher's master sender the clock-work mechanism operates a
contact arm which shows on the face of the sender in Fig. 480. There is
one contact for every station on the line. The clock at this office and
the clocks at all the waystation offices start together, and it is by
this means that the stations are signaled, as will be described later,
when the detailed operation of the circuits is taken up.
=Telephone Equipment.= Of no less importance than the selective devices
is the telephone apparatus. That which is here illustrated is the
product of the Western Electric Company, to whom we are indebted for all
the illustrations in this chapter.
_Dispatcher's Transmitter._ The dispatcher, in most cases, uses the
chest transmitter similar to that employed by switchboard operators in
every-day service. He is connected at all times to the telephone
circuit, and for this reason equipment easy for him to wear is
essential. In very noisy locations he is equipped with a double head
receiver. On account of the dispatcher being connected across the line
permanently and of his being required to talk a large part of the time,
there is a severe drain on the transmitter battery. For this reason
storage batteries are generally used.
[Illustration: Fig. 482. Waystation Desk Telephone]
_Waystation Telephones._ At the waystations various types of telephone
equipment may be used. Perhaps the most common is the familiar desk
stand shown in Fig. 482, which, for railroad service, is arranged with a
special hook-switch lever for use with a head receiver.
Often some of the familiar swinging-arm telephone supports are used, in
connection with head receivers, but certain special types developed
particularly for railway use are advantageous, because in many cases the
operator who handles train orders is located in a tower where he must
also attend to the interlocking signals, and for such service it is
necessary for him to be able to get away from the telephone and back to
it quickly. The Western Electric telephone arm developed for this use is
shown in Fig. 483. In this the transmitter and the receiver are so
disposed as to conform approximately to the shape of the operator's
head. When the arm is thrown back out of the way it opens the
transmitter circuit by means of a commutator in its base.
[Illustration: Fig. 483. Telephone Arm]
_Siding Telephones._ Two types of sets are employed for siding
purposes. The first is an ordinary magneto wall instrument, which
embodies the special apparatus and circuit features employed in the
standard waystation sets. These are used only where it is possible to
locate them indoors or in booths along the line. These sets are
permanently connected to the train wire, and since the chances are small
that more than one of them will be in use at a time, they are rung by
the dispatcher, by means of a regular hand generator, when it is
necessary for him to signal a switching.
[Illustration: Fig. 484. Weather-Proof Telephone Set]
In certain cases it is not feasible to locate these siding telephone
sets indoors, and to meet these conditions an iron weather-proof set is
employed, as shown in Figs. 484 and 485. The apparatus in this set is
treated with a moisture-proofing compound, and the casing itself is
impervious to weather conditions.
[Illustration: Fig. 485. Weather-Proof Telephone Set]
_Portable Train Sets._ Portable telephone sets are being carried
regularly on wrecking trains and their use is coming into more and more
general acceptance on freight and passenger trains. Fig. 486 shows one
of these sets equipped with a five-bar generator for calling the
dispatcher. Fig. 487 shows a small set without generator for conductors'
and inspectors' use on lines where the dispatcher is at all times
connected in the circuit.
[Illustration: Fig. 486. Portable Telephone Set]
[Illustration: Fig. 487. Portable Telephone Set]
These sets are connected to the telephone circuit at any point on the
line by means of a light portable pole arranged with terminals at its
outer extremity for hooking over the line wires, and with flexible
conducting cords leading to the portable set. The use of these sets
among officials on their private cars, among construction and bridge
gangs working on the line, and among telephone inspectors and repairmen
for reporting trouble, is becoming more and more general.
=Western Electric Circuits.= As already stated, a telephone
train-dispatching circuit may be from 25 to 300 miles in length, and
upon this may be as many stations as can be handled by one dispatcher.
The largest known number of stations upon an existing circuit of this
character is 65.
[Illustration: Fig. 488. Dispatcher's Station--Western Electric System]
_Dispatcher's Circuit Arrangement._ The circuits of the dispatcher's
station in the Western Electric system are shown in Fig. 488, the
operation of which is briefly as follows: When the dispatcher wishes to
call any particular station, he gives the key corresponding to that
station a quarter turn. This sends out a series of rapid direct-current
impulses on the telephone line through the contact of a special
telegraph relay which is operated by the key in a local circuit. The
telegraph relay is equipped with spark-eliminating condensers around its
contacts and is of heavy construction throughout in order to carry
properly the sending current.
_Voltage._ The voltage of the sending battery is dependent on the length
of the line and the number of stations upon it. It ranges from 100 to
300 volts in most cases. When higher voltages are required in order
successfully to operate the circuit, it is generally customary to
install a telegraph repeater circuit at the center of the line, in order
to keep the voltage within safe limits. One reason for limiting the
voltage employed is that the condensers used in the circuit will not
stand much higher potentials without danger of burning out. It is also
possible to halve the voltage by placing the dispatcher in the center of
the line, from which position he may signal in two directions instead of
from one end.
_Simultaneous Talking and Signaling._ Retardation coils and condensers
will be noticed in series with the circuit through which the signaling
current must pass before going out on the line. These are for the
purpose of absorbing the noise which is caused by high-voltage battery,
thus enabling the dispatcher to talk and signal simultaneously. The
250-ohm resistance connected across the circuit through one back contact
of the telegraph relay absorbs the discharge of the 6-microfarad
condenser.
[Illustration: Fig. 489. Selector Set--Western Electric System]
=Waystation Circuit.= The complete selector set for the waystations is
shown in Fig. 489, and the wiring diagram of its apparatus in Fig. 490.
The first impulse sent out by the key in the dispatcher's office is a
long direct-current impulse, the first tooth being three or four times
as wide as the other teeth. This impulse operates both magnets of the
selector and attracts their armatures, which, in turn, cause two pawls
to engage with the ratchet wheel, while the remaining quick impulses
operate the "stepping-up" pawl and rotate the wheel the requisite number
of teeth. Retardation coils are placed in series with the selector in
order to choke back any lightning discharges which might come in over
the line. The selector contact, when operated, closes a bell circuit,
and it will be noted that both the selector and the bell are operated
from battery current coming over the main line through variable
resistances. There are, of course, a number of selectors bridged across
the circuit, and the variable resistance at each station is so adjusted
as to give each approximately 10 milliamperes, which allows a large
factor of safety for line leakage in wet weather. The drop across the
coils at 10 milliamperes is 38 volts. If these coils were not employed,
it is clear that the selectors nearer the dispatcher would get most of
the current and those further away very little.
[Illustration: Fig. 490. Selector Set--Western Electric System]
A time-signal contact is also indicated on the selector-circuit diagram
of Fig. 490. This is common to all offices and may be operated by a
special key in the dispatcher's office, thereby enabling him to send out
time signals over the telephone circuit.
[Illustration: Fig. 491. Gill Dispatcher's Station]
=Gill Circuits.= The circuit arrangement for the dispatcher's outfit of
the Gill system is shown in Fig. 491. This is similar to that of the
Western Electric system just described. The method of operation also is
similar, the mechanical means of accomplishing the selection being the
main point of difference. In Fig. 492 the wiring of the Gill selector at
a waystation for local-battery service is shown. The selector contact
closes the bell circuit in the station and a few windings of this
circuit are located on the selector magnets, as shown. These provide the
"answer-back" by inductive means.
[Illustration: Fig. 492. Gill Selector--Local Battery]
Fig. 493 shows the wiring of the waystation, central-energy Gill
selector. In this case, the local battery for the operation of the bell
is omitted and the bell is rung, as is the case of the Western Electric
selector, by the main sending battery in the dispatcher's office.
[Illustration: Fig. 493. Gill Selector--Central Energy]
The sending keys of these two types of circuits differ, in that with the
local-battery selector the key contact is open after the selector has
operated, and the ringing of the bell must be stopped by the dispatcher
pressing a button or calling another station. Either of these operations
sends out a new current impulse which releases the selector and opens
its circuit.
With the central-energy selector, however, the contacts of the sending
key at the dispatcher's office remain closed after operation for a
definite length of time. This is obviously necessary in order that
battery may be kept on the line for the operation of the bell. In this
case the contacts remain closed during a certain portion of the
revolution of the key, and the bell stops ringing when that portion of
the revolution is completed. If, however, the dispatcher desires to give
any station a longer ring, he may do so by keeping the key contacts
closed through an auxiliary strap key as soon as he hears the
"answer-back" signal from the called station.
=Cummings-Wray Circuits.= The Cummings-Wray system, as previously
stated, is of the multiple-call type, operating with synchronous clocks.
Instead of operating one key after another in order to call a number of
stations, all the keys are operated at once and a starting key sets the
mechanism in motion which calls all these stations with one operation.
Fig. 494 shows the circuit arrangement of this system.
[Illustration: Fig. 494. Cummings-Wray System]
In order to ring one or more stations, the dispatcher presses the
corresponding key or keys and then operates the starting key. This
starting key maintains its contact for an appreciable length of time to
allow the clock mechanism to get under way and get clear of the
releasing magnet clutch. Closing the starting key operates the
clock-releasing magnet and also operates the two telegraph-line relays.
These send out an impulse of battery on the line operating the bridged
2,500-ohm line relays and, in turn, the selector releasing magnets;
thus, all the waystation clocks start in unison with the master clock.
The second hand arbor of each clock carries an arm, which at each
waystation is set at a different angle with the normal position than
that at any other station. Each of these arms makes contact precisely at
the moment the master-clock arm is passing over the contact
corresponding to that station.
If, now, a given station key is pressed in the master sender, the
telegraph-line relays will again operate when the master-clock arm
reaches that point, sending out another impulse of battery over the
line. The selector contact at the waystation is closed at this moment;
therefore, the closing of the relay contact operates the ringing relay
through a local circuit, as shown. The ringing relay is immediately
locked through its own contact, thus maintaining the bell circuit closed
until it is opened by the key and the ringing is stopped.
As the master-clock arm passes the last point on the contact dial, the
current flows through the restoring relay operating the restoring magnet
which releases all the keys. A push button is provided by means of which
the keys may be manually released, if desired. This is used in case the
dispatcher presses a key by mistake. Retardation coils and variable
resistances are provided at the waystation just as with the other
selector systems which have been described and for the same reasons.
The circuits of the operator's telephone equipment shown in Fig. 495,
are also bridged across the line. This apparatus is of high impedance
and of a special design adapted to railroad service. There may be any
number of telephones listening in upon a railroad train wire at the same
time, and often a dispatcher calls in five or six at once to give
orders. These conditions have necessitated the special circuit
arrangement shown in Fig. 495.
[Illustration: Fig. 495. Telephone Circuits]
The receivers used at the waystations are of high impedance and are
normally connected, through the hook switch, directly across the line in
series with a condenser. When the operator, at a waystation wishes to
talk, however, he presses the key shown. This puts the receiver across
the line in series with the retardation coil and in parallel with the
secondary of the induction coil. It closes the transmitter battery
circuit at the same time through the primary of the induction coil.
The retardation coil is for the purpose of preventing excessive side
tone, and it also increases the impedance of the receiver circuit, which
is a shunt on the induction coil. This latter coil, however, is of a
special design which permits just enough current to flow through the
receiver to allow the dispatcher to interrupt a waystation operator when
he is talking.
The key used to close the transmitter battery is operated by hand and is
of a non-locking type. In some cases, where the operators are very busy,
a foot switch is used in place of this key. The use of such a key or
switch in practical operation has been found perfectly satisfactory, and
it takes the operators but a short time to become used to it.
The circuits of the dispatcher's office are similarly arranged, Fig.
495, being designed especially to facilitate their operation. In other
words, as the dispatcher is doing most of the work on the circuit, his
receiver is of a low-impedance type, which gives him slightly better
transmission than the waystations obtain. The key in his transmitter
circuit is of the locking type, so that he does not have to hold it in
while talking. This is for the reason that the dispatcher does most of
the talking on this circuit. Foot switches are also employed in some
cases by the dispatchers.
=Test Boards.= It is becoming quite a general practice among the
railroads to install more than one telephone circuit along their
rights-of-way. In many cases in addition to the train wire, a message
circuit is also equipped, and quite frequently a block wire also
operated by telephone, parallels these two. It is desirable on these
circuits to be able to make simple tests and also to be able to patch
one circuit with another in cases of emergency.
[Illustration: Fig. 496. Test Board]
Test boards have been designed for facilitating this work. These consist
of simple plug and jack boxes, the general appearance of which is shown
in Fig. 496. The circuit arrangement of one of these is shown in Fig.
497. Each wire comes into an individual jack as will be noted on one
side of the board, and passes through the inside contact of this jack,
out through a similar jack on the opposite side. The selector and
telephone set at an office are taken off these inside contacts through a
key, as shown. The outside contacts of this key are wired across two
pairs of cords. Now, assume the train wire comes in on jacks _1_ and
_3_, and the message wire on jacks _9_ and _11_. In case of an accident
to the train wire between two stations, it is desirable to patch this
connection with a message wire in order to keep the all-important train
wire working. The dispatcher instructs the operator at the last station
which he can obtain, to insert plugs _1_ and _2_ in jacks _1_ and _10_,
and plugs _3_ and _4_ in jacks _3_ and _12_, at the same time throwing
the left-hand key. Then, obtaining an operator beyond the break by any
available means, he instructs him likewise to insert plugs _1_ and _2_
in jacks _9_ and _2_, and plugs _3_ and _4_ in jacks _11_ and _4_,
similarly throwing the left-hand key. By tracing this out, it will be
observed that the train wire is patched over the disabled section by
means of the message circuit, and that the selector and the telephone
equipment are cut over on to the patched connections; in other words,
bridged across the patching cords.
[Illustration: Fig. 497. Circuits of Test Board]
It will also be seen that with this board it is possible to open any
circuit merely by plugging into a jack. Two wires can be short-circuited
or a loop made by plugging two cords of corresponding colors into the
two jacks. A ground jack is provided for grounding any wire. In this
way, a very flexible arrangement of circuits is obtained, and it is
possible to make any of the simple tests which are all that are usually
required on this type of circuit.
=Blocking Sets.= As was just mentioned, quite frequently in addition to
train wires and message circuits, block wires are also operated by
telephone. In some cases separate telephone instruments are used for the
blocking service, but in others the same man handles all three circuits
over the same telephone. The block wire is generally a converted
telegraph wire between stations, usually of iron and usually grounded.
It seldom ranges in length over six miles.
[Illustration: Fig. 498. Blocking Set]
Where the block wires are operated as individual units with their own
instruments, it is unnecessary to have any auxiliary apparatus to be
used in connection with them. Where, however, they are operated as part
of a system and the same telephone is used on these that is used on the
train wire and message wire, additional apparatus, called a blocking
set, is required. This blocking set, shown in Figs. 498 and 499, was
developed especially for this service by the Western Electric Company.
As will be noted, a repeating coil at the top and a key on the front of
the set are wired in connection with a pair of train wire cords. This
repeating coil is for use in connecting a grounded circuit to a metallic
circuit, as, for instance, connecting a block wire to the train wire,
and is, of course, for the purpose of eliminating noise. Below the key
are three combined jacks and signals. One block wire comes into each of
these and a private line may be brought into the middle one. When the
next block rings up, a visual signal is displayed which operates a bell
in the office by means of a local circuit. The operator answers by
plugging the telephone cord extending from the bottom of the set into
the proper jack. This automatically restores the signal and stops the
bell.
[Illustration: Fig. 499. Blocking Set]
Below these signals appear four jacks. One is wired across the train
wire; one across the message wire; and the other two are bridged across
the two pairs of patching cords on each side of the set. The operator
answers a call on any circuit by plugging his telephone cord into the
proper jack.
If a waystation is not kept open in the evening, or the operator leaves
it for any reason and locks up, he can connect two blocks together by
means of the block-wire cords. These are arranged simply for connecting
two grounded circuits together and serve to join two adjacent blocks,
thereby eliminating one station. A jack is wired across these cords, so
that the waystation operator can listen in on the connection if he so
desires.
In some cases not only are the telephone circuits brought into the test
board, but also two telegraph wires are looped through this board before
going to the peg switchboard. This is becoming quite a frequent practice
and, in times of great emergency, enables patches to be made to the
telegraph wires as well as to the telephone wires.
=Dispatching on Electric Railways.= As interurban electric railways are
becoming more extended, and as their traffic is becoming heavier, they
approximate more closely to steam methods of operation. It is not
unusual for an electric railway to dispatch its cars exactly as in the
case of a steam road. There is a tendency, however, in this class of
work, toward slightly different methods, and these will be briefly
outlined.
On those electric railways where the traffic is not especially heavy, an
ordinary magneto telephone line is frequently employed with standard
magneto instruments. In some cases the telephone sets are placed in
waiting rooms or booths along the line of the road. In other cases it is
not feasible to locate the telephone indoors and then iron weather-proof
sets, such as are shown in Figs. 484 and 485, are mounted directly on
the poles along the line of railway. With a line of this character there
is usually some central point from which orders are issued and the
trainmen call this number when arriving at sidings or wherever they may
need to do so.
Another method of installing a telephone system upon electric railways
is as follows: Instead of instruments being mounted in booths or on
poles along the line, portable telephone sets are carried on the cars
and jacks are located at regular intervals along the right-of-way on the
poles. The crew of the car wishing to get in touch with the central
office or the dispatcher, plugs into one of these jacks and uses the
portable telephone set. At indoor stations, in offices or buildings
belonging to the railroad, the regular magneto sets may be employed, as
in the first case outlined.
On electric railway systems where the traffic is heavy, the train or car
movements may be handled by a dispatcher just as on the steam railroad.
There is usually one difference, however. On a steam road, the operators
who give the train crews their orders and manipulate the semaphore
signals are located at regular intervals in the different waystations.
No such operators are usually found on electric railways, except,
perhaps, at very important points, and, therefore, it is necessary for
the dispatcher to be able to signal cars at any point and to get into
communication with the crews of these cars. He does this by means of
semaphores operated by telephone selectors over the telephone line. The
telephone circuit may be equipped with any number of selectors desired,
and the dispatcher can operate any particular one without operating any
other one on the circuit. Each selector, when operated, closes a pair of
contacts. This completes a local circuit which throws the semaphore arm
to the "danger" position, at the same time giving the dispatcher a
distinctive buzz in his ear, which informs him that the arm has actually
moved to this position. He can get this signal only by the operation of
the arm.
Each semaphore is located adjacent to a telephone booth in which is also
placed the restoring lever, by means of which the semaphore is set in
the "clear" position by the crew of the car which has been signaled. The
wall-type telephone set is usually employed for this class of service,
but if desired, desk stands or any of the various transmitter arms may
be used.
It is necessary for the crew of the car which first approaches a
semaphore set at "danger," to get out, communicate with the dispatcher,
and restore the signal to the "clear" position. The dispatcher can not
restore the signal. The signal is set only in order that the train crew
may get into telephonic communication with the dispatcher, and in order
to do this, it is necessary for them to go into the booth in any case.
[Footnote A: We wish particularly to acknowledge the courtesy of the
Western Electric Company in their generous assistance in the preparation
of this chapter.]
REVIEW QUESTIONS
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 11--68
* * * * *
1. What are the advantages of a common-battery system?
2. When is the local battery to be preferred to the common-battery?
3. Enumerate the different kinds of line signals.
4. Make a diagram of the arrangement of a direct line lamp signal.
5. What is a direct line lamp with ballast? Give sketch.
6. Describe a line lamp with relay.
7. What is a pilot lamp and what are its functions?
8. Sketch three different kinds of batteries applied to cord circuits.
9. What is a supervisory signal?
10. Make diagram of a complete simple common-battery switchboard
circuit.
11. When will the supervisory signal become operative?
12. What is the candle-power of incandescent lamps used for line and
supervisory signals?
13. At what voltages do they operate?
14. What are visual signals?
15. Describe the mechanical signal of the Western Electric Company.
16. Give a short description of the general assembly of the parts of a
simple common-battery switchboard.
17. What is a transfer switchboard?
18. Outline the limitations of a simple switchboard.
19. Describe and sketch a plug-ended transfer line.
20. Why is the plug-seat switch not more widely adopted for use?
21. Make diagram of an order-wire arrangement.
22. What are the limitations of the transfer system?
23. What are the fundamental features of the multiple switchboard?
24. What is a multiple jack?
25. What is an answering jack?
26. Make a diagram showing the principle of multiple switchboards.
27. What is the busy signal?
28. What determines the size of a multiple switchboard?
29. What is the use of the intermediate distributing frame?
30. Make diagram of the series magneto multiple switchboard and describe
its operation.
31. What are the defects of this system?
32. Give a diagram of the branch terminal magneto multiple switchboard.
33. Give a diagram and a short description of the Monarch magneto
multiple switchboard.
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 69--134
* * * * *
1. Sketch and describe the line circuit of the common-battery multiple
switchboard of the Bell companies.
2. Make a diagram of the cord circuit of the Western Electric standard
multiple common-battery switchboard.
3. Describe the busy test in this system.
4. What is the function of the order-wire circuits?
5. What is jumper wire?
6. Give a short description of the relay mounting in the standard No. 1
relay board of the Western Electric Company.
7. What is the ultimate capacity of the No. 1 Western Electric
switchboard?
8. What is the capacity of the No. 10 Western Electric switchboard?
9. How does this switchboard No. 10 differ from No. 1?
10. Give a diagram of the two-wire line circuit of the Kellogg Company.
11. What is the capacity of the condenser of the cord circuit in the
foregoing system?
12. Give a complete diagram of the Kellogg two-wire board.
13. Describe the busy test in this system.
14. Give diagram of the Stromberg-Carlson multiple-board circuit.
15. What is the most important piece of apparatus in a multiple
switchboard?
16. What is the spacing of the multiple jacks in the No. 1 Western
Electric switchboard?
17. How do the relays of the Western Electric Company differ from those
of other companies?
18. Describe the relay construction of the Monarch Telephone Company.
19. What is meant by inter-office trunking?
20. What is the present practice in America as to the capacity of
multiple hoards?
21. What is the tendency in Europe regarding the capacity of multiple
boards?
22. Discuss the preferences in American practice.
23. State the different methods of trunking between exchanges.
24. When are two-way trunks employed?
25. Make diagram of the Western Electric inter-office connection system.
26. Describe the standard four-party line trunk ringing key of the
Western Electric Company.
27. Sketch and describe a keyless trunk.
28. Give diagram of the inter-office connection of the Kellogg system.
29. How does this system differ from the Western Electric in regard to
the ringing?
30. Why are the A and B switchboards in large exchanges entirely
separated?
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 135--226
* * * * *
1. What is the general object of automatic telephone systems?
2. What are the common arguments against these systems and how are they
met?
3. Give the operations that the calling subscriber has to go through in
any one of the successful systems.
4. During calling what is happening at the central office?
5. Describe the action of the Strowger or Automatic Electric Company
selecting switch.
6. What is the function of a line switch?
7. Describe the Strowger scheme of trunking and illustrate its action by
diagram.
8. Make a diagram of the sub-station apparatus and connections.
9. Make a diagram of the line switch unit.
10. Describe the action of the various guarding features necessary to
protect a busy line.
11. Make a simple diagram of the circuits of the first selector.
12. Give the functions and operations of the connector.
13. Give a diagram of connecting circuits.
14. Tell all you can regarding the battery supply to the connected
subscriber.
15. How are subscribers disconnected after they are through talking?
16. Describe a multi-office system.
17. Give a diagram of circuits of the trunk repeater.
18. Make a complete diagram of the connections between a calling and a
called subscriber in an automatic system.
19. What is the rotary connector?
20. Describe the sub-station equipment of the Lorimer automatic system.
21. Describe the Lorimer central-office apparatus.
22. Give a description of the progress of a call from its institution to
the final disconnection in the Lorimer system.
23. What is the automanual system?
24. Give general features of the operation in the automanual system.
25. Describe the automanual system subscribers' apparatus.
26. Give a description of the automanual central-office equipment.
REVIEW QUESTIONS
ON SUBJECT OF TELEPHONY
PAGES 227--270
* * * * *
1. What kinds of currents are employed?
2. What types of power plants are used?
3. Describe the sources of current supplied for the operator's
transmitter current and ringing current.
4. Make a diagram of the Warner pole changer.
5. Make a diagram of pole changers for harmonic ringing.
6. What is a multi-cyclic generator set?
7. Make a diagram of governor for harmonic ringing generators.
8. Describe the various primary sources of power.
9. Make a diagram of the mercury-arc-rectifier circuits.
10. What provision against breakdown is made?
11. Tell all you can about the storage battery--its construction and its
operation.
12. What is a pilot cell?
13. Describe the switches, meters, and protective devices used on the
power switchboard.
14. Give a diagram showing a typical example of a common-battery manual
switchboard equipment and circuits.
15. Give the main points concerning the construction of a central-office
building.
16. What provision should be made for cable runways?
17. Make a sketch of a small central-office floor plan.
18. Describe the Western Electric main and intermediate frames. Give
diagrams.
19. Give principal points regarding small office terminal apparatus.
20. Give types of line circuits.
21. Describe the typical equipment of a large manual office. Give floor
plans.
22. Give floor plan of an automatic office.
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 271--320
* * * * *
1. What is a private-branch exchange?
2. What does "P. B. X." mean?
3. What is the function of the private-branch exchange operator?
4. Describe the key type of a small private-branch exchange switchboard.
5. Describe the different methods of supervision of private-branch
connections.
6. Describe the automatic equipment of the common-battery type in
private-branch exchanges.
7. How is secrecy of individual lines obtained in a private-exchange
equipment?
8. What is an intercommunicating system?
9. Sketch a magneto intercommunicating system.
10. Sketch and describe a plug type common-battery intercommunicating
system.
11. Sketch and describe the action of the push button in the Monarch
system and in the Western Electric system.
12. Sketch and describe the Monarch intercommunicating system.
13. What is the office of the junction box in this system?
14. What is a long-distance message?
15. What is the function of the repeating coil in the long-distance
line?
16. Which is the simplest form of long-distance switch?
17. What is a phantom circuit?
18. Under what control is the ringing of the subscriber in
long-distance calls?
19. What is meant by ticket passing?
20. What particular advantage has a common-battery set on long-distance
lines?
21. Give a typical load curve for telephone traffic.
22. Why is traffic a study of importance?
23. State the function of the intermediate distributing frame.
24. State the different methods of traffic study.
25. What is the trunking factor?
26. Define _trunking efficiency_.
27. Enumerate some of the elements upon which the quality of service in
a manual system depends.
28. What is team work?
29. How does the cost of telephone service vary?
30. What two general methods of charging for telephone service are in
use?
31. Describe a calculagraph and how is it used?
32. How are toll connections timed by the Monarch Telephone Company?
33. Sketch and describe the Western Electric Company line circuit and
service meter.
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 321--358
* * * * *
1. Describe a phantom circuit with diagram.
2. Explain how two phantoms may be joined by a physical circuit.
3. Which are the better, phantom or physical circuits, and why?
4. Explain how the simplex circuit differs from the phantom telephone
circuit.
5. Why are not telegraph wires as serviceable for telephone work as
telephone wires are for telegraph work?
6. Give the names of the different parts of a railway composite set and
explain method of operating.
7. State the causes of the introduction of the telephone into the train
dispatching field and explain the advantages it has over the telegraph
for this work.
8. In transmitting orders for train dispatching, how are mistakes
avoided?
9. Describe the Western Electric selector and explain its use.
10. In what way does the Gill selector differ from the Western Electric?
11. What special feature does the multiple coil selector possess?
12. What special arrangement is provided for the train dispatcher in
noisy locations?
13. How can a man on a wrecking train get connection with the train
dispatcher?
14. What is the usual limit in length of a telephone train dispatching
circuit and what is the largest number of stations at present existing
on such a circuit?
15. What is the voltage of the sending battery for a train dispatcher's
circuit and upon what is it dependent?
16. For what purpose is a repeater circuit used?
17. How is the noise caused by a high voltage battery absorbed so that
the dispatcher may talk and signal simultaneously?
18. Draw a diagram showing the circuit arrangement for the dispatcher's
outfit of the Gill system.
19. Explain fully the purpose of the retardation coil in connection with
a waystation set.
20. In case of accident to a train wire between two stations, how can
the connection be patched if the road is also equipped with a message
circuit in addition to the train wire?
21. Why do some railroads have block wires in addition to train wires
and message circuits?
22. If a waystation on a block wire is to be cut out for any length of
time, by what method can the two adjacent blocks be connected,
eliminating the station between?
23. What are some of the methods used for dispatching on electric
railways where the traffic is not especially heavy?
24. On an electric road in case a car approaches a semaphore set at
"danger," what must the crew of the car do?
INDEX
_The page numbers of this volume will be found at the bottom of the
pages; the numbers at the top refer only to the section._
A
Automanual system 218
automatic distribution of calls 223
automatic switching equipment 222
building up a connection 224
characteristics of 218
operation 219
operator's equipment 220
setting up a connection 224
speed in handling calls 224
subscriber's apparatus 219
Automatic desk stand 158
Automatic Electric Company's telephone system 149
automatic sub-offices 201
connector 185
function of 185
location of 186
operation of 186
first selector operation 179
function of line switch 152
line switch 153, 163
bridge cut-off 173
circuit operations 167
guarding functions 173
line and trunk contacts 164
locking segment 172
master switch 171
relation of, to connectors 174
structure of 166
summary of operation 174
trunk ratio 165
trunk selection 165
multi-office system 196
party lines 202
release after conversation 196
rotary connector 202
second selector operation 182
selecting switches 153, 175
release mechanism 178
side switch 175
subdivision of subscribers' lines 152
subscribers' station apparatus 158
operation 160
bell and transmitter springs 160
ground springs 160
impulse springs 161
release springs 163
ringing springs 163
salient points 163
trunking 154
connector action 157
first selector action 156
line switch action 154
second selector action 156
two-wire automatic systems 203
two-wire and three-wire systems 157
underlying feature of trunking system 153
Automatic telephone systems 135
arguments against 135
attitude of public 141
complexity 136
expense 140
flexibility 140
subscriber's station equipment 142
automatic vs. manual 143
comparative costs 142
definition 135
methods of operation 143
fundamental idea 147
grouping of subscribers 145
local and inter-office trunks 148
Lorimer system 144
magnet vs. power-driven switches 144
Automatic telephone systems
methods of operation
multiple vs. trunking 145
outline of action 146
Strowger system 143
testing 148
trunking between groups 145
Automatic wall set 158
B
Blocking sets 355
Busy test 48
busy-test faults 50
potential of test thimbles 49
principle 49
C
Circuits 321
applications 322
composite 326
phantom 321
transmission over 324
transpositions 323
railway composite 327
ringing 327
simplex 324
Common-battery multiple switchboard 69
assembly 106
Dean multiple board 93
cord circuit 94
line circuit 93
listening key 94
ringing keys 94
test 94
Kellogg two-wire multiple board 84
battery feed 88
busy test 90
complete cord and line circuit 88
cord circuit 86
line circuit 85
summary of operation 91
supervisory signals 87
wiring of line circuit 92
multiple switchboard apparatus 97
jacks 99
lamp jacks 100
relays 101
Stromberg-Carlson multiple board 96
cord circuit 96
supervisory signals 97
test 97
Western Electric No. 1 relay board 69
capacity range 80
cord circuit 71
functions of distributing frames 77
line circuit 69
modified relay windings 79
operation 72
operator's circuit detail 75
order-wire circuits 78
pilot signals 79
relay mounting 80
testing--called line busy 75
testing--called line idle 74
wiring of line circuit 76
Western Electric No. 10 board 80
circuits 81
economy 84
operation 83
test 83
Common-battery switchboard 11
advantages of operation 11
common battery vs. magneto 12
cord circuit 20
battery supply 20
complete circuit 21
supervisory signals 21
cycle of operations 23
jacks 30
lamps 24
mounting 25
line signals 14
direct-line lamp 14
direct-line lamp with ballast 15
line lamp with relay 17
pilot signals 17
mechanical signals 27
Kellogg 28
Monarch 28
Western Electric 27
relays 28
switchboard assembly 31
Composite circuits 326
Connector 185
Cord circuit 20
Cord circuit
battery supply 20
complete circuit 21
supervisory signals 21
Cord-rack connectors 66
Cummings-Wray selector 342
D
Dean multiple board 93
Dispatchers' keys 339
Dispatching on electric railways 356
G
Gill selector 341
H
Housing central-office equipment 249
arrangement of apparatus in small manual offices 252
combined main and intermediate frames 253
floor plans for 252
types of line circuits 255
automatic offices 267
typical automatic office 270
central-office building 249
fire hazard 249
provision for cable runways 251
provision for employes 251
size of building 250
strength of building 250
large manual office 256
I
Intercommunicating systems 282
common-battery systems 283
Kellogg plug type 284
Kellogg push-button type 285
Monarch system 287
Western Electric system 285
definition 282
limitations 282
for private-branch exchanges 290
simple magneto system 282
J
Jacks 30
K
Kellogg mechanical signal 28
Kellogg trunk circuits 125
Kellogg two-wire multiple board 84
Keyboard wiring 67
L
Lamp mounting 25
Lamps 24
Line signals 14
direct-line lamp 14
direct-line lamp with ballast 15
line lamp with relay 17
pilot signals 17
Line switch 163
Long-distance switching 293
definitions 293
center-checking 297
operators' orders 294
by call circuits 294
by telegraph 294
particular party calls 295
switching through local board 293
ticket passing 296
trunking 295
high-voltage toll trunks 295
through ringing 295
two-number calls 294
use of repeating coil 293
waystations 297
Lorimer automatic system 144, 205
central-office apparatus 208
connective division 210
sectional apparatus 209
switches 213
interconnector 214
interconnector selector 214
primary connector 213
rotary switch 213
secondary connector 214
signal transmitter controller 214
operation 215
subscriber's station equipment 206
M
Magneto multiple switchboard 53
branch-terminal multiple board 58
arrangement of apparatus 61
magnet windings 61
operation 60
field of utility 53
modern magneto multiple board 63
assembly 66
cord circuit 64
test 62
Magneto multiple switchboard
series-multiple board 54
defects 57
operation 56
Measured service 310
local service 316
meter method 316
prepayment method 318
ticket method 316
rates 310
toll service 311
long haul 311
short haul 311
timing toll connections 312
units of charging 311
Mechanical signals 27
Kellogg 28
Monarch 28
Western Electric 27
Mercury-arc rectifier circuits 237
Monarch visual signal 28
Multi-office exchanges, necessity for 109
Multiple switchboard 43
busy test 48
cord circuits 46
diagram showing principle of 47
double connections 46
field of each operator 51
field of utility 43
influence of traffic 52
line signals 45
multiple feature 43
P
Phantom circuit 321
Pilot signals 17
Plug-seat switch 38
Pole changers for harmonic ringing 231
Power plants 227
auxiliary signaling currents 233
currents employed 227
alternating current 227
direct current 227
operator's transmitter supply 228
power plant circuit 248
power switchboard 246
meters 246
protective devices 248
switches 246
primary sources 234
charging from direct-current mains 234
charging dynamos 235
mercury-arc rectifiers 236
rotary converters 234
provision against breakdown 237
capacity of power units 238
duplicate charging machines 238
duplicate primary sources 238
duplicate ringing machines 238
ringing-current supply 229
magneto generators 229
pole changers 229
ringing dynamos 232
storage battery 239
initial charge 241
installation 240
low cells 244
operation 242
overcharge 243
pilot cell 243
regular charge 244
replacing batteries 245
sediment 245
types 227
common-battery systems 228
magneto systems 228
Power switchboard 246
Private-branch exchanges 271
with automatic offices 278
secrecy 279
battery supply 279
circuits, key-type board 276
definitions 271
desirable features 281
functions of the private-branch exchange operator 272
marking of apparatus 281
private-branch switchboards 273
common-battery type 273
cord type 275
key type 275
magneto type 273
ringing current 280
supervision of private-branch connections 277
R
Relays 28
Rotary connector 202
S
Selecting switches 175
Selector 175
Simplex circuits 324
Storage battery 239
Storage cell 240
Stromberg-Carlson multiple board 96
Strowger automatic system 143
Subscribers' board 259-261
Switchboard assembly 31
T
Table
automanual system time data 225
automatic systems, messages per trunk in 305
calling rates 302
long-distance groups, messages per trunk in 305
manual system, messages per trunk in 304
out-trunking, effect of, on operator's capacity 303
subscribers' waiting time 226
Telephone traffic 298
importance of traffic study 300
methods of traffic study 301
observation of service 308
quality of service 305
accuracy and promptness 307
answering time 306
busy and don't answer calls 307
courtesy and form 307
disconnecting time 306
enunciation 308
team work 308
rates of calling 300
representative traffic data 302
calling rates 302
operators' loads 302
toll traffic 304
trunk efficiency 303
trunking factor 303
traffic variations 298
busy hour ratio 299
unit of traffic 298
Telephone train dispatching 333
advantages 335
apparatus 338
Cummings-Wray selector 342
dispatcher's transmitter 343
Gill selector 341
portable train sets 345
siding telephones 345
waystation telephones 344
Western Electric selector 338
blocking sets 355
causes of its introduction 334
Cummings-Wray circuits 350
on electric railways 356
Gill circuits 349
railroad conditions 337
rapid growth 333
test boards 353
transmitting orders 337
waystation circuits 348
Western Electric circuits 347
Telephone train-dispatching circuit
Cummings-Wray 350
Gill 349
waystation 348
Western Electric 347
Test boards 353
Transfer switchboard 34
field of usefulness 41
handling transfers 38
limitations 40
plug-seat switch 38
transfer lines 35
jack-ended trunk 35
plug-ended trunk 37
Trunking in multi-office systems 109
classification 112
one-way trunks 103
two-way trunks 112
Kellogg trunk circuits 125
necessity for exchanges 109
Western Electric trunk circuits 116
W
Warner pole changer 230
Waystation telephones 344
Western Electric
mechanical signal 27
selector 338
trunk circuits 116
Transcriber's Notes.
Spelling variants where it wasn't possible to determine the author's
intent were left as is. These include: "clockwork" and "clock-work;"
"doorkeeper" and "door-keeper;" "interrelation" and "inter-relation;"
"multicyclic" and "multi-cyclic;" "redesign" and "re-design," along with
derivatives.
Added closing double quote in Steinmetz entry in list of authorities:
"Theoretical Elements of Electrical Engineering."
Changed "switch-hook" to "switch hook" on page 88: "the subscriber's
switch hook."
Page 107 says there is room for 300 banks of 100 multiple jacks, but
then says this allows for 3,000 multiple jacks in all, rather than
30,000. Based on the figure, 300 banks should be 30 banks, which would
correct the arithmetic. However, I did not change this.
Changed "bi-paths" to "by-paths" on page 185: "circuits or by-paths."
Changed "appararus" to "apparatus" on page 209: "The sectional
apparatus."
Changed "two number" to "two-number" on page 312: "the two-number calls
are ticketed."
On page 333, a paragraph begins with "It has been only within the past
three few." Perhaps the author meant "It has been only within the past
three years" or "It has been only within the past few years." But since
I didn't know, I left is as is.
Changed "them ain" to "the main" on page 333: "on the main line."
Changed "weatherproof" to "weather-proof" on page 357: "iron
weather-proof sets."
Changed "interoffice" to "inter-office" three times on page 364, to
match the spelling in the body of the document: "meant by inter-office
trunking;" "inter-office connection system;" "of the inter-office
connection."
Changed "break-down" to "breakdown" on page 367: "provision against
breakdown."
Changed "way-station" to "waystation" twice on page 372: "with a
waystation set;" and "a waystation on a block wire."
Changed "way stations" to "waystations" on page 375, in the entry for
Long-distance switching.
Each page of the Index repeated this text: "Note.--For page numbers see
foot of pages." They were removed.