Importance

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Abstract

In a key telephone system of the type that uses the tip and ring conductors of a telephone line to transmit a hold condition control signal between stations, interstation signal-generating and detecting circuitry are provided at first and second stations, respectively, for enabling the first station to actuate, during a hold condition on the line, an audible signalling device, such as a buzzer, located at the second station. The interstation signal is generated on command by selective actuation of a hold switch button at the first station, and is transmitted over the line as an altered hold control signal, which is detected at the second station. Upon such signal detection, a buzzer is energized alerting the second station to the presence of a held call on the line.

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First Claim