The Mosler Safe Company

American Standard Inc.

Robert S Bayer

Mark A Petronaci

A quadrature demodulator for a phase shifted input pulse signal. The demodulator produces a four state digital code word on two output lines dependent upon the phase of the input signal. The input signal may have a phase shift, from the phase of the carrier signal, of zero degrees, +90.degree., -90.degree., or 180.degree.. The demodulator includes a clock-driven counter having an output signal at a fundamental frequency substantially identical to the carrier frequency of the input pulse signal. The counter produces additional output signals at frequencies which are multiples of the carrier frequency. The counter is synchronized with the input signal during a reference interval of zero phase shift, and a strobe circuit combines the various counter outputs to produce strobe signals to detect the phase shifted input signal. The strobe signals are used to clock a pair of flip-flops which each receive the input signal at a data input, with the Q outputs of the flip-flops providing the pair of output lines which indicate the four states of the digital code word.

Phase shift demodulator

Protected objects are connected together to form an antenna. Preferably, the cabinet for the detector circuitry is also included in the antenna. The antenna is excited by a voltage controlled oscillator (VCO). The capacitive reactance of the antenna changes when an intrusion occurs. This causes the frequency of the VCO signal to undergo an instantaneous change. A phase comparator compares the phase of the VCO signal with the phase of a reference oscillator signal. An instantaneous change in the frequency of the VCO signal due to a change in the capactive reactance of the antenna when an intrusion occurs is reflected by a shift in phase between the VCO signal and the reference oscillator signal. This causes the phase comparator signal to change. A deriving means, preferably including a dual differentiator circuit, which derives the rate of the rate of change of the phase comparator signal, and a differential comparator, which is triggered by the dual differentiator circuit in the event of an intrusion, activates a signaling circuit so as to produce an alarm when an intrusion occurs. Since the antenna is connected to the VCO and there is no bidirectional coupling between the VCO and the reference oscillator, the electronic security apparatus is incapable of defeat by connection of a frequency generator to the antenna, because inherent drift in the reference oscillator eventually produces an alarm. Additional features are also disclosed.

Capacitive intrusion detector circuitry utilizing reference oscillator

An intercom system for remote banking which facilitates communication between a teller terminal and a remotely located customer terminal. A two-way speaker is provided at the customer location and a separate microphone and a speaker are provided at the teller location. An amplifier in the communication path linking the two stations is connected such that normally its input is responsive to the customer two-way speaker with its output feeding the teller speaker, permitting the customer to talk to the teller. When the teller speaks into the microphone, and assuming certain conditions are met, the amplifier automatically switches to connect the teller microphone to the amplifier input and the customer two-way speaker to the amplifier output, permitting the teller to talk to the customer. To avoid switching communication direction in response to noise at the teller location, the system is additionally provided with a noise microphone located at the teller station for transducing ambient noise thereat, and means responsive to the output of the noise and teller microphones for switching the system to the teller speech transmission mode only when a source of teller speech is located within a predetermined region enclosing the teller speech microphone, which region excludes therefrom the noise microphone. Switching of the system to the teller speech transmission mode occurs, assuming a teller speech source is located within the predetermined region surrounding the teller microphone, notwithstanding that a source of noise is present, providing the noise source is located exteriorly of said predetermined region.

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West Milford, NJ, United States of America

Robert S Bayer