Telephone system testing apparatus and techniques utilizing central measuring equipment with a plurality of remote test stations

摘要

Centralized telephone circuit testing equipment with receptacles for selectively receiving a wide variety of electronic circuit modules, various modules being provided to make the equipment capable of performing a large number of commonly employed telephone tests. A scanning system is disclosed as part of the central measuring equipment for determining which of a plurality of remote testing stations has requested access to the central measuring equipment, one requesting remote station at a time being given complete control over a test function of the central measuring equipment for conducting tests on a telephone trunk. Improvements are also disclosed in the individual test function electronic circuit modules, including common circuits for use in measuring both signal level and circuit noise, a logarithmic analog-to-digital convertor capable of handling signals that cross zero dBm in level, round off digital display circuits to improve accuracy of the display and to aid in calibrating the instruments, and an improved frequency measuring circuit.