Automatic attenuation monitor for telephone lines - has period measuring cct. and comparator evaluating transmitted freq. sweep

摘要

The automatic attenuation monitor, for telephone lines, transmits signals over a given frequency band to a remote evaluating receiver. The receiver contains a period measuring circuit supplied with a first signal whose frequency corresponds to the frequency of the voltage detected at the end of the line and with a second signal whose frequency corresponds to this voltage's amplitude. The period measuring circuit output is compared with two alternately-switched signal sequence: the first sequence consists of a number of stored, sequential signal values following the direction of the frequency sweeps at the transmitter and corresponding to transitions between frequency tolerance values; and the second sequence consists of signal values whose direction corresponds to tolerance values in the same direction.