THE NEW YORK-LONDON TELEPHONE CIRCUIT 749 



network is dissipated; that part which enters the delay circuit is 

 transmitted through it, with small attenuation, to the end. Here it 

 meets with a reflecting termination and is transmitted back whence 

 it came. Reaching the hybrid coil, half of it goes back toward the 

 input and half of it is transmitted on in the desired direction. The 

 half which goes to the input meets the output side of a one-way am- 

 plifier and is dissipated. The remaining half passes through an am- 

 plifier which makes up for the transmission loss of the delay circuit 

 and the loss due to the two divisions of energy at the hybrid coil. 



The desirability of maintaining the proper relationships between the 

 time actions of the relays and the delays in the other parts of the system 

 will be apparent from the foregoing. A circuit for measuring the time 

 of operation of the relays is provided which in combination with a 

 detector and a relay may also be used for measuring the time required 

 for alternating currents to travel through a delay network or other 

 telephone circuit. This device is capable of measuring directly time 

 intervals as short as .0001 second and up to 1 second in length. The 

 measuring device is conveniently located along with the apparatus com- 

 prising the voice-operated device, as shown in Fig. 4. 



In conclusion, it should be pointed out that the method of operation 

 that has been described is expensive and has disadvantages which 

 make it undesirable on any but a very special and necessarily complex 

 telephone circuit, such as the transatlantic. It has, however, proved 

 satisfactory in this service. The more interesting effects which this 

 method of operation accomplishes may be restated as follows: 



Given the condition of an anti-singing circuit such as the New York- 

 London radio circuit, it is possible to make the amount of power 

 radiated from the radio transmitting stations independent of the 

 strength of the voice currents arriving over the land lines. For ex- 

 ample, a subscriber speaking from a suburb of Chicago is heard just as 

 loudly in London as another person speaking from the terminal of the 

 circuit at New York. 



As a result, voices of all talkers, strong or weak, are heard with 

 the same freedom from static. 



Both of the above effects result from the adjustment of the strength 

 of outgoing speech so as to load the radio transmitter to maximum 

 output for all messages. If the circuit were operated with amplifica- 

 tion fixed at a value required by the strongest talkers, then the voices 

 of weak speakers would often be lost unless the power of the radio 

 transmitter were increased several hundred fold. 



