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.

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.

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.

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.

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.

ToC

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 THE 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?

ToC

INDEX

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