Lamp control circuit for key telephone systems
AssigneeInternational Telephone and Telegraph Corporation
InventorCoy Edwin Matheny
Life of this patent
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Abstract
A circuit is provided for detecting the condition of a signalling output being applied by a line circuit to a key telephone and for responding to a predetermined condition of the line circuit. The detecting circuit provides a comparison with the signalling output to identify the signalling output and produce an indication based on the condition signalled by the output. The input to the lamp circuit comparator is compared for amplitude and wave form with a reference for passage of the output signal. With the circuit configuration disclosed, a large range of amplitudes may be used as a basis for comparison in a plurality of wave forms.
Claims5
In a key telephone system, a circuit for detecting the condition of a line in the system, in which the line may be in one state in which a line lamp representing that line is being pulsed by a signal comprised of current interrupted at a first rate, or in a second rate state in which the lamp is being pulsed by a signal comprised of current interrupted at a second rate, said circuit including means receptive of a current signal directed toward the line lamp, means for receiving a reference signal at a predetermined amplitude and at an interrupted predetermined one of said rates, means for comparing the rate of the signal directed toward said lamp against the predetermined signal rate, and means responsive to the rate of the signal directed toward said lamp and said predetermined reference signal being essentially identical for producing an output reaction indicative of the signal directed toward the lamp.
In a key telephone system including a station having a plurality of lines terminating thereat with each of said lines having a respective line circuit, a line lamp associated with each line circuit, a circuit for detecting signals at one of a plurality of interrupted signalling rates applied to a lead to a line lamp of one of said lines, including a source of signals at a predetermined one of said rates, means for comparing signals received from said source against the signals applied to the lamp lead of said one line, and output means responsive to the signals of the same rate being compared in said comparing means for emitting an output signal indicative of the identity of the rates of said signals, and means responsive to a predetermined condition of a conductor at said line circuit indicative of the status of said line for passing said output signal, and a bi-stable device switched to its active state responsive to the passing of said output signal.
Dependencies are inferred from the claim text.