ber'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

C