REFERENCE SYSTEM FOR TELEPHONE TRANSMISSION 553 



line, consisting of balanced resistance networks, has a uniform fre- 

 quency response characteristic. The characteristic of the complete 

 system, therefore, except as its level is affected by the attenuation in the 

 reference line, is that of the reference transmitter and reference re- 

 ceiver combined, there being no reflection effects at the junctions of 

 the reference line with either the reference transmitter or receiver. 



Fig. 11 shows the effect of introducing distortion networks in both 

 the reference transmitter and reference receiver. The distortion net- 



500 1000 



FREQUENCY 



2000 3000 



Fig. 11— Response characteristics of reference transmitter and receiver 

 with distortion networks. 

 A = Reference transmitter — db — ^1.0 volt per bar. 

 B = Reference receiver — db — ^1.0 bar per volt. 



work introduced in the reference transmitter simulates the distortion 

 in the transmitter, station set and cord circuit, of the standard cable 

 reference system. Similarly, the distortion network introduced in the 

 reference receiver simulates the distortion of the receiver, station set 

 and cord circuit, of the standard cable reference system. These two 

 networks are designated, respectively. Transmitter Distortion Net- 

 work No. 1 and Receiver Distortion Network No. 1. The distortion 

 of any transmitter, receiver, or station set may be similarly simulated 



