AUTOMATIC TESTING OF INTERTOLL TRUNKS 945 



ily. The far-end then repeats Steps 2 and 3 for another trial. The test 

 frame at the near end will stop and sound an alarm after a third unsuc- 

 cessful attempt. 



If the trunk loss in the near-to-far direction exceeds 10 db, the loss in 

 the transmitting pad at the far end will exceed 10 db. Under this condi- 

 tion the far end will, prior to Step 3, remove 10 db loss from the trans- 

 mitting pad to increase the test power level on the trunk. This is done to 

 improve the test power level-to-noise ratio and to reduce the error when 

 measuring losses of intertoll trunks having apparatus whose loss is de- 

 pendent on signal amplitude. The far end will also return to the near 

 end a short on-hook signal. This on-hook signal at the near end, just 

 prior to Step 3, is an "add 10" signal and causes the near end to add 10 

 db to its loss measurement in Step 3, to compensate for the loss which 

 Avas removed at the far end. 



Immediately after Step 3, if the transmission test control key on the 

 test frame is in the transmission only position, the test frame will cause 

 the teletypewriter to record the results of the measurements and will 

 then break down the connection and advance to the next trunk. If the 

 transmission test control key is in the transmission and noise position, the 

 test frame will wait after Step 3 for each end to complete a noise check 

 in Step 4. 



816^4 



For Step 4 the near-end removes its near-far amplifier and the near-far 

 and far-near receiving pads and increases the gain of the amplifier-recti- 

 fier for a noise check at the near-end. Likewise, the far-end removes the 

 receiving pads and increases the gain of the amplifier-rectifier for a noise 

 check at the far end. Each end rests in this condition while the amplifier- 

 rectifier at each end integrates the noise voltage over a 5-second interval. 

 If the integrated value of noise voltage at either end exceeds a pre- 

 determined value, the amplifier-rectifier at that end will operate measur- 

 ing relay (m) in its output which causes a high noise condition to be 

 registered at that end. If neither end registers a high noise condition, 

 the test call proceeds to completion without a noise indication being 

 recorded at the near end. 



When the transmission measuring and noise checking circuit at the 

 far end completes the noise check, it releases itself from the test line and 

 is then free to serve a new call while the test line returns an on-hook 

 signal to notify the originating end that the test is completed. This will 

 be either a steady on-hook signal if the far end has not registered a high 



