SWITCHING EQUIPMENT 589 



man that the generator attendant has received the signal and also 

 just what signal he received. The switchboard operator, after 

 having seen this returned signal, will push the button at the left 

 of the transmitter handle, which will extinguish the lamp and cut 

 out the signal bell. This completes the cycle of sending and 

 receiving a signal. 



The system is identical to that used on the Panama Canal to 

 indicate the position of the lock machinery. 



The signal system in any important station is always sup- 

 plemented by a multiple-station intercommunicating telephone 

 system. This is used when special orders or instructions are to be 

 given. 



Multi-recorder. The multi-recorder is a device for recording 

 on a strip of paper the exact time of the occurrence of any elec- 

 trical phenomena and is applicable in central stations for record- 

 ing switching operations, line surges and other disturbances 

 beyond the control of the operator. In case of accidents such a 

 record is of particular value because it enables the engineer to know 

 where and when the trouble started and how the switching was 

 done. 



The recorder consists essentially of a number of stamps operated 

 by a clockwork and printing the time, within fraction of seconds, 

 of the event to which they are relayed. A description of this device 

 is given by Prof. E. E. F. Creighton in the A.I.E.E Transactions, 

 1912, page 825. 



Oil Circuit Breaker Batteries. The operation of remote-con- 

 trol oil circuit breakers, field switches, field rheostats, signal lights, 

 etc., necessitate an absolutely reliable source of energy which 

 should be entirely independent of the regular distribution circuits 

 and held in reserve exclusively for this purpose. 



It is therefore usual to ftistall a motor-generator set consisting 

 of an induction motor driven by power from the A.C. circuit, 

 direct connected to a direct-current generator. In order, however, 

 to insure continuity of service in case of an interruption in the 

 supply of current from this machine, whether due to failure of 

 the power supply on the A.C. circuit or to some derangement 

 in the machine itself, it is standard practice to install a storage 

 battery, which is normally kept floating across the terminals of 

 the direct-current machine- This motor generator is kept run- 

 ning continuously except for such brief periods of time when it may 



