Telephone socket tester - makes closed circuit through socket capacitor and strap to test same and includes line searcher detecting signal generated by tester

摘要

The appts. is used partic. for ensuring the correct operation of the socket capacitor and wiring strap, without requiring removal of the socket cover. A telephone pin is engageable in the socket and coupled through a polarity inverter to a Darlington transistor pair connected in series with a light emitting diode and 50 mA current limiting resistor. The inverter permits electrical inversion of the capacitor poles to generate diode flashes indicating correct capacitor operation. A diac (13) safeguards against excessive externally applied currents. The instrument also includes a line seeker which has two electrode probes interconnected by a light emitting diode continuously illuminated when probes detect signal in a line being tested, a shunt diac protecting the diode. The pin (14) also includes a switch (9) enabling the line to be isolated by shorting during use of the instrument.