Test apparatus for a subscriber line

摘要

An apparatus for enabling the performance loop resistance and DC balance checks on a subscriber line includes relay contacts coupled across the line terminals. The apparatus includes circuitry for detecting the application of an activating signal to the line and for optically coupling a resulting trigger signal to a pair of monostable timers. The timer output pulses are arranged so that the relay is energized subsequent to the removal of the activating signal and remains energized during an interval established by the relative durations of the timer output pulses.