Line finder for a common control telephone exchange

Claim 1

In a telephone exchange, a subscribers'' line finder operable in combination with a line circuit, the combination comrpising a line circuit biased and switched to provide varying voltage levels depending on the status of the associated subscriber''s line; means in said line circuit responsive to the summation of said voltage levels and of interrogation pulses from an interrogation device to produce selected further potentials; said further potentials representing status of subscriber''s lines, i.e., either the condition or the situation of subscriber''s line associated with a line circuit; where the condition refers to whether the line is looped or unlooped and situation refers to whether the line is parked or not parked; means responsive to said further potentials to provide appropriate read signals; a logic combination circuit; said logic combination circuit including means to receive further signals representing a demand for a search for service requests or a search for parked lines; said logic combination circuit responding to said read signals and to said further signals to provide additional signals representing either the condition of the lines served by said line finder or their situation; and means for applying said further signals to control circuits of the line finder; whereby the line finder may be used alternatively for detecting and indicating service requests and faulty lines.