Hold detecting and control circuit for a key telephone system

Details Hold detecting and control circuit for a key telephone system Hold detecting and control circuit for a key telephone system

1987-03-06

1989-02-07

Ng, Jin F.

Telephonic communications

Multi-line or key substation system with selective switching...

Detail of hold circuitry

379164, 379377, 379393, H04M 100, H04M 906

Patent

active

048037184

ABSTRACT:
A key telephone system for use with at least two telephone lines that extend between a central office and two or more telephone stations. Each station is capable of responding to a manually-actuated hold select switch by establishing a hold condition on one of the lines and by connecting a line terminating impedance across the line that is to be held. Each station is further capable of monitoring the state of each line, and indicating the state of each line, without applying any indicating signals to the telephone lines. Each station furthermore determines threshold voltages for on-hook, off-hook and hold line states and determines line state by comparison of line voltage with such threshold voltages.

REFERENCES:
patent: 3914556 (1975-10-01), Frazee
patent: 4004106 (1977-01-01), Yachabach
patent: 4011413 (1977-03-01), Phillips
patent: 4132860 (1979-01-01), Rasmussen
patent: 4133985 (1979-01-01), Rasmussen et al.
patent: 4382163 (1983-05-01), White

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