556 BELL SYSTEM TECHNICAL JOURNAL 



cable reference system. These transmitting elements were connected 

 in turn to a 24-mile standard cable line terminated by the reference 

 receiver with its distortion network, the receiver being adjusted in 

 accordance with the results of the first series of tests. In the third 

 and fourth series of tests the master reference system with the dis- 

 tortion networks in both the transmitter and receiver was compared 

 with the standard cable reference system, the line of the master 

 system serving as the adjustable element. These two series of tests 

 were similar except that 24 miles of standard cable were used in one 

 series of tests and 14 miles of standard cable in the other. The adjust- 

 ments for the reference transmitter and reference receiver in these 

 tests were those determined from the first and second series. From 

 the results obtained in the third and fourth series of tests, the magni- 

 tudes were determined of the reflection gain at the junction of the 

 standard cable line with either the reference transmitter or the reference 

 receiver, and of the volume equivalent of 1 mile of standard cable in 

 terms of db. The reference transmitter and reference receiver, each 

 with its distortion network, were then readjusted in accordance with 

 these data. The fifth series of tests served as a check on the results 

 of the previous four series. In this fifth series, the master reference 

 system with transmitter and receiver distortion networks and 24 db 

 in the line was compared with the standard cable reference system 

 with 24 miles of standard cable in its line. 



In the sixth series of tests the adjustment of the reference receiver 

 without distortion was determined to make it equivalent on a volume 

 basis to the reference receiver with distortion. The reference trans- 

 mitter with distortion and the reference line with 24 db formed the 

 rest of the system during these comparisons. In the seventh series 

 of tests the sound output of the master reference system without 

 distortion was compared to the sound output of this same system with 

 distortion networks in the reference transmitter and reference re- 

 ceiver, the reference transmitter being adjusted to obtain a balance. 

 During these tests 24 db was kept in the reference line. The final 

 series of tests, serving as a check on all of the above determinations, 

 consisted of a comparison between the master reference system with- 

 out distortion and the standard cable reference system, the line of 

 the master system being adjusted in making this comparison. 



In making voice tests to determine the above settings, the speaker, 

 whose position with respect to the transmitters was kept constant, 

 called standard testing sentences in a conversational tone. A given 

 intensity of calling was maintained by watching the deflections on a 

 volume indicator connected across the output of the transmitting 



