Ring trip circuit for subscriber telephone

Details Ring trip circuit for subscriber telephone Ring trip circuit for subscriber telephone

H - Electricity

04

M

379/16

H04M 19/02 (2006.01) H04M 3/02 (2006.01)

Patent

CA 1291835

RING TRIP CIRCUIT FOR SUBSCRIBER TELEPHONES ABSTRACT OF THE DISCLOSURE Disclosed is an improved ring trip circuit for a subscriber telephone, for detecting an on-hook state or an off-hook state of the telephone. The ring trip circuit can be formed in a small size and can be formed by an LSI. The ring trip circuit includes a voltage detecting circuit, for detecting a voltage difference between both ends of a ringer sending resistor and having a circuit converting the voltage difference to a current difference, the voltage difference varying in response to an on-hook state or an off-hook state of the telephone, and a state detecting circuit for detecting the on-hook state or the off-hook state in response to a value of the voltage difference. The voltage detecting circuit is formed by a plurality of current mirror circuits, each of which includes at least two transistors. The state detecting circuit includes a comparator circuit formed by a plurality of transistors.

569791

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