Importance

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Abstract

A telephone in-use indicator having a diode bridge which is connected to a telephone line. The diode bridge ensures than an input signal from the telephone line is at a constant polarity. An inverter is connected to the diode bridge and receives a signal from the telephone line through the diode bridge. The inverter operates to invert the signal received from the telephone line. An oscillator receives a signal output from the inverter. A light emitting diode is connected to an output of the oscillator and is intermittently driven by the oscillator. A power source powers the inverter, oscillator and light emitting diode. When one telephone extension along the telephone line is changed from an 'on-hook' to an 'off-hook' condition, a drop in voltage is detected. As a result, the light emitting diode is intermittently driven by the oscillator to thereby provide an indication that a telephone line is in use.

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First Claim