US 4,490,583 AGranted

Plural line telephone controller

AssigneeCircom, Inc.

InventorsJohn J. Bednarz, William T. Bloodworth

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Abstract

A telephone controller for connecting a single-line telephone in a local N-line system with other telephones equipped with similar controller comprises N interface units each connecting one telephone line to a dual conductor telephone bus in turn connected to the telephone. Each interface unit includes an off-hook/ring detector connected to the telephone line served by that unit, a hold latch to connect a load of predetermined impedance across the telephone line to simulate an off-hook condition, a hold bus driver connected to a hold bus line extending to all system controllers, a telephone line condition indicator lamp that indicates on-hook, off-hook, incoming ring and hold conditions on the line, a line switch for connecting the telephone line to the telephone bus, an activity monitor to detect an off-hook condition for the telephone bus attributable to the associated telephone line, a telephone condition indicator lamp actuated by the activity monitor, a line selector switch, and line switch control circuits to close the line switch in response to actuation of the line selector switch and to keep it closed in response to detection of an off-hook condition by the activity monitor. The controller also comprises a hold switch, a hold latch control that actuates a hold latch when the hold switch is operated coincident with detection of an off-hook condition by the activity monitor associated with that hold latch, audible signal means to signal an incoming call, and a conference switch enabling conference calls.

A telephone controller for connecting a single-line telephone to any one of N two-conductor telephone lines, in a local system including a plurality of other single-line telephones equipped with similar controllers, the controller comprising:

a two-conductor telephone bus connected to the input/output terminals of the telephone;
monitor means for detecting an off-hook condition of the telephone;
N interface units each connecting one of the telephone lines to the telephone bus, each interface unit comprising:
off-hook/ring detector means for detecting off-hook and incoming ring signal conditions on the telephone line;
hold latch means actuatable between an unlatched passive condition and a latched hold condition in which the hold latch means connects and maintains a load of predetermined impedance across the telephone line conductors to simulate an off-hook condition;
a telephone line condition indicator connected to the off-hook/ring detector means and to the hold bus line, for visually indicating on-hook, off-hook, incoming ring and hold conditions on the telephone line;
line switch means for connecting the telephone line to the telephone bus;
a line selector switch;
line switch control means for closing the line switch means in response to actuation of the line selector switch;
and line bridge means for maintaining the line switch means closed in response to detection of an off-hook condition by the monitor means;
the telephone controller further comprising:
a hold switch;
hold latch control means, connected to the hold switch and having an input connection from the activity monitor means and output connections to the hold latch means
in each interface unit of the controller, for actuating any one of the hold latch means to its latched hold condition upon operation of the hold switch coincident with detection of an off-hook condition by the activity monitor means for the same telephone line as that hold latch means;
and audible signal means, having input connections from the off-hook/ring detector means in each interface unit, for generating an audible signal whenever an incoming ring signal is detected on any of the N telephone lines.

12 more elements

Abstract

Claims37