Circuit for telephone set comprising a light-emitting diode powe

Details Circuit for telephone set comprising a light-emitting diode powe Circuit for telephone set comprising a light-emitting diode powe

1996-09-27

1998-04-21

Zele, Krista

Telephonic communications

Subscriber line or transmission line interface

Network interface device

396399, H04M 172

Patent

active

057426767

ABSTRACT:
A circuit comprising a transistor (T1) is connected in series to a resistor (RM) for measuring the line current; the whole is connected to the terminals (1,2) of the line. According to the invention, a light-emitting diode (18) is connected in series to a variable current source (20), the whole being connected in parallel to the emitter/collector path of the transistor (T1), and the variable current source, which receives a monitoring signal that represents the line current, produces a current that varies between a zero current and a maximum current for an average line current that varies between a low threshold and a high threshold.

REFERENCES:
patent: 4151377 (1979-04-01), Whitaker
patent: 4564729 (1986-01-01), Mills
patent: 4648109 (1987-03-01), Boeckman
patent: 4723279 (1988-02-01), Field
patent: 5170429 (1992-12-01), Stocklin
patent: 5422947 (1995-06-01), Azem
patent: 5570421 (1996-10-01), Morishima
"TEA1062", Low Voltage Telephone Transmission Circuit With Dialler Interface, marketed by Philips, Sep. 1989.

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