Electronic telephone exchange line meter pulse counter - operates with subscribers appts. to produce standard sized pulses utilising two operational amplifiers and discrete components

摘要

The circuit utilizes an operational amplifier (OP1) with associated RC filter and a logorithmic operational amplifier (OP2) to produce pulses at output (A) which are independent of the incoming pulse level. Preferably, a field effect transistor (T2) between the input to the operational amplifier (OP1) and output (A) stabilizes the output level. A switching transistor (T1) detects exchange line current and, in conjunction with zener diode (Z) produces a supply voltage (U). Transistor (T1) is a constant current source which provides high inductance for the speed circuit. ADVANTAGE - Current drain is negligible in given state.