Electronic telephone call timer

Claim 1

A timing and display unit for use with an individual telephone set having a receiver and a hook switch cradle and for providing an indication of the elapsed time of individual call intervals and an indication of the cumulative use time of said telephone set, said unit comprising: power supply means for generating a reference supply voltage, a gated clock signal train and a reference frequency signal from an AC line source, said power supply means having a gated reference frequency signal input terminal; call timer and display means coupled to said power supply means for generating a visible indication of the elapsed time of an individual call interval, said call timer and display means including a first counter; cumulative timer and display means coupled to said power supply means for generating a visible indication of the cumulative use time of said telephone set, said cumulative timer and display means including a second counter; and telephone off-hook sensor means including a source of electromagnetic radiation and a radiation sensitive element positioned to detect the presence or absence of said receiver on said cradle and having first and second input terminals coupled to said reference frequency signal and said reference supply voltage, respectively, and first and second input terminals coupled to said gated reference frequency signal input terminal of said power supply means and said call timer and display means, respectively, for generating said gated reference frequency signal and a gated reset signal in response to said receiver being placed in an off-hook condition, said call timer and display means including means responsive to the generation of said gated reset signal for initializing said first counter.