High-Frequency Measurements of Communication Lines

This paper describes briefly a testing technique which has been developed for making line measurements at high frequencies in connection with the application of carrier telephone and telegraph systems in the Bell System. The measurement of line attenuation, impedance, and cross-talk up to frequencies as high as 50,000 cycles is described, using a number of specially developed and standardized high-frequency apparatus units. These include an oscillator, a detector-amplifier, an impedance bridge, a thermomilliammeter set, a variable attenuator, a cross-talk set, and a frequency meter. A brief description of the individual units is given, as well as their coordinated use in complete testing circuits.