Automatic telephone dialer for use in intrusion detection systems

Claim 1

In an automatic dialer of the type used to access a telephone line to transmit a prerecorded message via said line to a called location, said called location having a predetermined telephone number manifested by a series of predetermined tone signals of a specified frequency, which signals are stored on a tape associated with said dialer, which tape also contains said prerecorded message, the combination therewith of apparatus for responding to said tone signals to generate dial pulses of a sufficient duration of an on and off time to dial said number via said line to access said called location, comprising: (a) a controllable element positioned in series with said telephone line and controllable in a first position to close for engaging said line and in a second position to disengage said line, (b) detection means responsive to said series of tone signals for providing a pulse output indicative of the format of the tone signals stored on said tape, (c) a multivibrator having at least a first output and a clock input adapted to receive a pulse for changing the output condition of said multivibrator, said multivibrator operative in a first mode wherein said first output is high (SWITCH-ON) and operative in a second mode (SWITCH-OFF) wherein said first output is low, a data input associated with said multivibrator and operative to cause said output to assume a high or a low condition upon receipt of a clock pulse at said clock input, wherein said output will assume either said high or low condition according to the level impressed upon said data input as being high or low, (d) means coupling said output of said detector means to said data input of said multivibrator, (e) timing means having one input coupled to said data input of said multivibrator and a second input coupled to said output of said multivibrator, said timing means operative to provide a predetermined delayed signal at an output when said data input signal is different from said output signal of said multivibrator, to provide a pulse at an output of said timing means, (f) means coupling said output of said timing means to the clock input of said multivibrator for applying said pulse to said clock input of said multivibrator to cause said output of said multivibrator to assume the level present at said data input, and (g) means coupling said output of said multivibrator to said controllable element to operate the same alternatively in said first and second positions according to said timing means and said tone bursts as detected to thereby provide said dialing pulses to said telephone line at a predetermined on and off ratio.