Importance

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Abstract

There is disclosed an input condition sensing circuit for use in a facility management system which is selectively operable in a first mode for sensing the presence or absence of a voltage potential or a second mode for sensing a high or low impedance and which provides a binary output signal indicative of the condition being sensed and an amplifier coupled to the input for generating a control signal having an amplitude relating to the input condition being sensed. The circuit also includes detecting means coupled to the amplifier for providing a binary output in response to the control signal and indicative of the condition being sensed and select means coupled to the detecting means for selectively conditioning the circuit for operating in either the first or second mode. The select means is arranged to cause the detecting means to provide a first binary output state in response to sensing the presence of a voltage while in the first operating mode and a cause the detecting means to provide a different binary output state in response to sensing a high impedance while in the second operating mode.

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First Claim