256 



BELL SYSTEM TECHNICAL JOURNAL 



the delays in the two paths are different a relative phase shift proportional 

 to the difference will appear in the two beat notes. This phase change can 

 be measured with a phase shifter in the beat note circuit or with a phase 

 shifter which varies the relative phase of the two signals fed to one branch 



ATTENUATORS 



MEASURING BRANCH 



OSCIL- 

 LATORS 



fj 



f 



NETWORK 



TO BE 

 MEASURED 



DETECTOR 



AMPLIFIER 



PHONES 



1-MC 

 FREQUENCY 

 STANDARD 



CATHODE- RAY 

 OSCILLOSCOPE 



ATTENUATORS 



DELAY 



BALANCING 



LINE 



DETECTOR 



PHASE 

 SHIFTER 



AMPLIFIER 



REFERENCE BRANCH 



Fig. 8 — Schematic circuit for the precise measurement of delay in the intermediate 

 frequency range. 



DETECTOR 



CATHODE-RAY 

 OSCILLOSCOPE 



DETECTOR 



Fig. 9 — Simplified circuit electrically equivalent to the circuit of Fig. 8 



as compared with the relative phase of the two signals fed to the other 

 branch. Figure 8 shows how the coaxial slider can be used for the latter 

 type of measurement. 



The simplified diagram of Fig. 9 will be used to show how the delay of the 

 unknown network can be calculated in terms of this circuit. It will be 

 assumed that the electrical lengths of the paths AF and BF are equal so 



