Telephone call timer

Claim 1

A timer unit for telephone calls comprising an energy source, counter means driven by an oscillator for generating timing signals for establishing time periods for use in generating tonal signals of different frequencies to provide an audible indication of the expiration of fixed time limits after the initiation of a telephone call, the signals of one frequency indicating the start of the time period and periodic one minute intervals during the time period including the end of said selected time period and the signals of another frequency indicating a time interval of approximately 21/2 minutes after initiation of the call circuit means connected to said counter means and responsive to said timing signals for providing the audible indication of the start of the time period, the periodic intervals during the time period, including the end thereof, and the occurrence of the 21/2 minute time interval, said circuit means including a first and a second logic circuit and a programmable decoder having an input connected to a first output of the counter means, an output of said decoder being connected to an input of said second logic circuit, a second output of said counter means being connected to an input of said first logic circuit, an OR gate, the output of said first and said second logic circuits being connected to first and second inputs of said OR gate, said OR gate having a third input connected to receive a third output from said counter and said OR gate having its output connected to activate said signal source so as to provide a first tonal output signal of said one frequency responsive to an output from said first logic circuit and a second tonal output of said another frequency responsive to an output from said second logic circuit whereby said second tonal output provides a warning signal prior to completion of the 3 minute time period.