Subscriber line impedance measurement method and measuring circu

Details Subscriber line impedance measurement method and measuring circu Subscriber line impedance measurement method and measuring circu

1997-01-06

1998-10-06

Loomis, Paul

Telephonic communications

Diagnostic testing, malfunction indication, or electrical...

Testing of subscriber loop or terminal

379 24, 324603, 324522, H04M 308, H04M 322, H04M 124, G08B 2300

Patent

active

058189050

ABSTRACT:
A measurement method and measuring circuit are described for high-speed measurement of subscriber line impedance without the influence of counter electromotive force of the bell circuit or hum noise. A measurement current is supplied from a controlled-current source to each of a pair of subscriber lines by way of switches, and subscriber line voltage and current values are measured during the transient state. A measurement time interval is divided into a first-half and a second-half interval, the average values of the voltage and current are detected for each time interval, and moreover, the difference between voltages at the beginning and end of each time interval is detected. In this case, the controlled-current source is controlled by a control means such that the rate of change of the current value over time remains at or below a fixed value. The combined equivalent resistance and equivalent capacitance of subscriber lines and terminals are then computed using the detected values according to a preset numerical formula.

REFERENCES:
patent: 4853950 (1989-08-01), Crane
patent: 5444759 (1995-08-01), Vogt, III et al.
patent: 5465287 (1995-11-01), Egozi
patent: 5661776 (1997-08-01), Charland

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