IX-BAND SINGLE-FREQUENCY SIGNALING 



1323 



ward signal because the far end receiver at this time has a long operate 

 time. 



The signal receiver is connected in series with the receiving hraiich 

 of the voice transmission path and is provided with a voice amplifier lo 

 provide a l)lo(*king function so noises originating in the switciiing eciuip- 

 ment or beyond will not interfere with operation of the sigiuding receiver, 

 and to compensate for the signaling l)ri(lging loss. 



The receiving portion of the circuit is shown in the central and lower 

 portions of Fig. 8. The idle condition of the trunk is shown, tone is being 

 received, the r, rg and rf relays are operated and the band elimination 

 filter is inserted in the receiving l)ranch to prevent signaling tone from 

 entering a connected circuit and interfering with signaling there. 



The signal cm-rents coming in from the line are passed through the 

 signal amplifier, limiter and low pass filter and applied to the signal- 

 guard netW'Ork from which signal voltage is applied to the dc amplifier 

 tube to operate the above mentioned relays and open the e lead, which 

 extends into the trunk circuit. Typical wave forms at several points in 

 the circuit are shown in Fig. 9. The extra operate time provided during 

 the talking condition is obtained from slow relays (not shown) W'hich at 

 this time are in the path from the r to the rg relay. These relays also 

 change the sensiti\-ity, and guard ratio. 



INCOMING SIGNAL 



RECTIFIED SIGNAL 

 VOLTAGE e,, FIG. 8 



r 



r 



RELAY 

 OPERATES \ 



RECTIFIED GUARD 

 VOLTAGE Qz^ FIG. 8 



NET VOLTAGE AT 

 DC AMPLIFIER 



OUTPUT SIGNAL 

 (NO CORRECTION) 



Fig. 'J — Tj-pical wave forms in 1,600-cycle receiver. 



