Importance

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Abstract

Apparatus for monitoring usage of a telephone connected across tip and ring terminals of a telephone system. The apparatus includes status circuitry operative under microprocessor control to repetitively sample the voltage across the tip and ring terminals and to examine the sampled voltages to determine whether the telephone is in an on/hook condition or an off/hook condition. When the telephone is in an off/hook condition an output of a first value is produced by the status circuitry, and when the telephone is in an on/hook condition an output of a second value is produced by the status circuitry. The microprocessor examines the outputs to detect the occurrence of transitions in the outputs between the first and second values representing transitions between on/hook and off/hook conditions of the telephone. For each detected transition, an activity timer within the microprocessor is set to a count corresponding to a predetermined activity-monitoring time period and decremented at a predetermined rate. In the event the activity timer times out, an alarm condition is produced. Thus, so long as the telephone is used during the activity-monitoring time period an alarm condition will be prevented.

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First Claim