Apparatus for applying particular voltages to three-terminal circuits and measuring resulting current flows for the purpose of determining circuit characteristics

摘要

Apparatus which may be used in the performance of at least six tests on a telephone subscriber's line is disclosed. The apparatus operates to force the tip and ring leads of a line to particular potential levels and then produces output voltages related to the currents flowing in the tip and ring leads. These output voltages may be processed to perform the following test: dc Thevenin, ac three-terminal admittance, ac foreign emf, percent imbalance, swept loaded loop and detection of unauthorized equipment. The apparatus may be used when performing tests on other three-terminal circuits.