904 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1953 



the system a single systematic shape, which will be small in magnitude 

 at the equalizing points because the different settings of this control in 

 successive line repeaters will tend to cancel out. This setting of output 

 beta circuit gain is controlled by a gain adj switch accessible from out- 

 side the amplifier housing. The adjustment mil be made on an in-service 

 basis as part of normal maintenance procedures, using the level at each 

 repeater of one of the system pilot frequencies (3,096 kc) as the index 

 of proper setting. 



Manufacturing Testing 



As mentioned above, the mechanical design of the amplifier has been 

 planned to permit the separate testing of the five gain-determining net- 



0.6 



o 



z 

 < 

 I 

 o 



Z -0.4 



< 



^-0.6 



— ^^^.s 



0.2 



0.3 



0.4 0.5 0.6 0.8 1.0 2 3 4 



FREQUENCY IN MEGACYCLES PER SECOND 



5 6 



Fig. 15 — Amplifier gain versus output beta circuit misalignment adjust- 

 ment. 



works, the tuned interstage of the input amplifier, and the separate 

 input and output amplifiers before their assembly with the regulating 

 network to form complete amplifiers. Variations in environment are 

 minimized by the use of jigs which also make it unnecessary, in general, 

 to solder to the network under test. Visual gain sets which cover the 

 transmitted band and are accurate to two or three hundredths db are 

 used. The component network or component amplifier under test is 

 connected in series with a complementary or equalizing network to 

 obtain a flat transmission characteristic which can be accurately com- 

 pared to the transmission of standard attenuators. The completely 

 assembled ampUfiers are similarly tested. Quality control charts of the 

 resulting measurements on all components are useful in detecting shifts 

 in transmission whi(!h might be caused by loss of control in element 

 manufacture or by shifts of element values caused by subsequent damage 

 in handling. 



