Intrusion alarm system for use with two-wire-cable

An intrusion alarm system having a plurality of units capable of being interconnected by a cable having only two conductors for detecting the presence of an intruder in a protected area, the system comprising:

• a plurality of ultrasonic transmitting units;
• a plurality of ultrasonic receiving units;
• a control unit including:
• signal means for applying an ultrasonic frequency AC signal to said two conductors of said cable;
• means for applying DC power to said two conductors;
• and
• means for detecting an alarm signal applied to said two conductors by one of said receiving units and for producing an alarm indication in response to the detection of an alarm signal;
• means for connecting said plurlaity of transmitting units to said cable conductors at various locations in said protected area and responsive to the AC signal on said conductors for transmitting an ultrasonic signal into respective locations in the protected area;
• and
• means for connecting said plurality of receiving units to said cable conductors at said various locations, each said receiving unit including:
• sensor means for receiving echoes of the transmitted ultrasonic signal in its respective area and for producing an output electric signal representative thereof;
• processing means energized by said DC power on said two conductors and responsive to said sensor means output electric signals and said AC signal on said two conductors to detect signals representative of echoes produced by an intruder for producing an output signal representative thereof;
• alarm means operable for applying said alarm signal to said cable conductors in response to said output signal from said processing means representative of an intruder presence for producing said alarm indication at said control unit wherein each of the alarm means includes means for increasing the current drawn from the cable conductors by the receiving unit to provide the alarm signal, each of the processing means including means responsive to the AC signal on the two cable conductors for synchronously demodulating the sensor means output signal,
• wherein the control unit further includes means for amplitude modulating the ultrasonic AC signal applied to the cable conductors at a modulation frequency lower than the ultrasonic frequency;
• and
• wherein the processing means includes means for detecting echoes having a frequency component equal to the modulation frequency to distinguish false alarm echoes.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit and transmitting units being interconnected by a cable, over which cable the control unit sends an ultransonic AC signal to the transmitting units, a control unit for providing a modulated AC signal at an ultransonic frequency which is modulated at a lower modulation frequency, the control unit comprising:

• a first signal source for providing a reference signal at the ultrasonic frequency;
• a second signal source for providing a signal at the modulation frequency;
• power control means for providing a pulse-width-modulated output signal having a frequency twice that of the ultrasonic frequency and having a duty cycle which is variable in response to a modulation control signal;
• means for combining the power control means output signal with the reference signal to provide a digital output signal having a fundamental component at the ultrasonic frequency, the amplitude of which varies as a function of the duty cycle of the power control means output signal;
• and
• means responsive to the modulation frequency signal for providing the modulation control signal.

An intrusion alarm system having a plurality of units capable of being interconnected by a cable having only two conductors for detecting the presence of an intruder in a protected area, the system comprising:

• a plurality of ultrasonic transmitting units;
• a plurality of ultrasonic receiving units;
• a control unit including:
• signal means for applying an ultrasonic frequency AC signal to said two conductors of said cable;
• means for applying DC power to said two conductors;
• and
• means for detecting an alarm signal applied to said two conductors by one of said receiving units and for producing an alarm indication in response to the detection of an alram signal;
• means for connecting said plurality of transmitting units to said cable conductors at various locations in said protected area and responsive to the AC signal on said conductors for transmitting an ultrasonic signal into respective locations in the protected area;
• and
• means for connecting said plurality of receiving units to said cable conductors at said various locations, each said receiving unit including:
• sensor means for receiving echoes of the transmitted ultrasonic signal in its respective area and for producing an output electric signal representative thereof;
• and
• processing means energized by said DC power on said two conductors and responsive to said sensor means output electric signals and said AC signal on said two conductors to detect signals representative of echoes produced by an intruder for producing an output signal representative thereof;
• and
• alarm means operable for applying said alarm signal to said cable conductors in response to said output signal from said processing means representative of an intruder presence for producing said alarm indicating at said control unit, wherein the signal means includes a modulator for providing a modulated AC signal of an ultrasonic frequency which is modulated at a lower modulation frequency comprising:
• a first signal source for providing a reference signal at the ultrasonic frequency;
• a second signal source for providing a signal at a modulation frequency;
• power control means for providing a pulse-width-modulated output signal having a frequency twice that of the ultrasonic frequency and having a duty cycle which is variable in response to a modulation control signal;
• means for combining the power control means output signal with the reference signal to provide a digital output signal having a fundamental component at the ultrasonic frequency, the amplitude of which varies as a function of the duty cycle of the power control means output signal;
• and
• means responsive to the modulation frequency signal for providing the modulation control signal.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the AC signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• demodulating means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presence of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm means, including an indicator operable to increase the current drawn from said cable, responsive to the detecting means output signal for operating said indicator and applying said increased current as said alarm signal to the cable for remotely indicating the detection of an intruder.

An intrusion alarm system having a plurality of units capable of being interconnected by a cable having only two conductors, for detecting the presence of an intruder in any of a plurality of areas, the system comprising:

• a control unit including:
• signal means for applying an ultrasonic frequency AC signal to said two cable conductors;
• means for applying DC power to said two cable conductors;
• and
• means for detecting an alarm signal applied to the two cable conductors by a receiving unit and for producing an alarm indication in response to the detection of an alarm signal;
• a plurality of transmitting units connected to the cable conductors and responsive to the AC signal thereon for transmitting an ultrasonic signal into respective areas;
• and
• a plurality of receiving units, each connected to the cable conductors and including:
• sensor means for receiving echoes of the transmitted signal and for producing an output signal representative thereof;
• processing means, responsive to sensor means output signals representative of echoes produced by an intruder, for producing an output signal representative thereof;
• and
• alarm means for applying an alarm signal to the cable conductors in response to output signals from the processing means representative of an intruder presence;
• wherein each of the alarm means includes means for increasing the current drawn from the cable;
• and
• wherein the alarm means includes a light and means responsive to the alarm signal for connecting the light across the cable to illuminate the light and increase the current drawn by the receiving unit from the cable.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the AC signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• demodulating means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presence of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm means responsive to the detecting means output signal for applying an alarm signal to the cable indicating the detection of an intruder;
• wherein the connecting means includes:
• a transformer having two primary windings and a secondary winding;
• a capacitor connected in series between one terminal of opposite polarity of each primary winding;
• the second terminals of each primary winding being respectively connected to the two conductors of the cable;
• the DC power for the receiving unit being taken from across the capacitor;
• and
• means connected to the transformer secondary winding for providing the reference signal.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presence of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm means responsive to the detecting means output signal for applying an alarm signal to the cable indicating the detection of an intruder;
• wherein the connecting means includes:
• a transformer having two primary windings and a secondary winding;
• a capacitor connected in series between one terminal of opposite polarity of each primary winding;
• the second terminals of each primary winding being respectively connected to the two conductors of the cable;
• the DC power for the receiving unit being taken from across the capacitor;
• and
• means connected to the transformer secondary winding for providing the reference signal;
• including:
• a tuned circuit, of which the secondary winding is a part, having a resonance frequency equal to the frequency of the AC signal on the cable conductors so that the transformer primary windings connected across the cable conductors present a high impedance at the frequency of the AC signal.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the AC signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• demodulating means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presence of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm means, including an indicator operable to increase the current drawn from said cable, responsive to the detecting means output signal for operating said indicator and applying said increased current as said alarm signal to the cable for remotely indicating the detection of an intruder;
• wherein the demodulating means includes:
• two demodulator circuits, each having first and second inputs and providing an output signal;
• means for applying the transducer output signal to the first inputs of each demodulator circuit;
• means, responsive to the reference signal, for applying quadrature-related reference signals of the same frequency as the AC signal to the second inputs of the first and second demodulators respectively;
• a phase difference network responsive to the output signals from the first and second demodulators for shifting the phase of one of the demodulator output signals by 90.degree. of the reference frequency with respect to the other demodulator output signal to provide two output signals;
• and
• means for demodulating one of the phase difference network output signals with the other of the phase difference output signals.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the AC signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• demodulating means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presentce of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm-means responsive to the detecting means output signal for applying an alarm signal to the cable indicating the detection of an intruder;
• wherein the demodulating means includes:
• two demodulator circuits, each having first and second inputs and providing an output signal;
• means for applying the transducer output signal to the first inputs of each demodulator circuit;
• means, responsive to the reference signal, for applying quadrature-related reference signals of the same frequency as the AC signal to the second inputs of the first and second demodulators respectively;
• a phase difference network responsive to the output signals from the first and second demodulators for shifting the phase of one of the demodulator output signals by 90.degree. of the reference frequency with respect to the other demodulator output signal to provide two output signals;
• and
• means for demodulating one of the phase difference network output signals with the other of the phase difference output signals;
• wherein the signal transmitted by the transmitting units is modulated at a modulation frequency lower than the frequency of the AC signal, and wherein the detection means further includes:
• filter means responsive to signals having a component at the modulation frequency for providing an output signal;
• and
• means for applying the demodulating means output signal to the filter means.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the AC signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• demodulating means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presence of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm means responsive to the detecting means output signal for applying an alarm signal to the cable indicating the detection of an intruder;
• a latch circuit having alarm and non-alarm states and providing an output signal representative of the state of the latch;
• means for setting the latch to the alarm state in response to a signal from the detection means representative of a detected intruder;
• and
• means responsive to the latch output signal for providing an output indication when the latch is in the alarm state;
• further including means responsive to a momentary absence of DC power across the conductors of the cable for resetting the latch to the non-alarm state.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the AC signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• demodulating means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presence of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm means responsive to the detecting means output signal for applying an alarm signal to the cable indicating the detection of an intruder;
• wherein the demodulating means includes:
• three transistors, the emitters of each of the transistors being connected;
• means responsive to the transducer output signal for applying a current to the connected transistor emitters representative of the transducer output signal;
• means for applying the reference signal between the base terminal of a first one of the transistors and the base terminal of a second one of the transistors;
• and
• means for differentiating the reference signal and for applying the differentiated reference signal between the base terminal of the first transistor and the base terminal of the third transistor;
• the signals present at the collector terminals of the second and third transistors being quadrature-demodulated output signals having a 90.degree. phase shift therebetween.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the AC signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• demodulating means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presence of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm means responsive to the detecting means output signal for applying an alarm signal to the cable indicating the detection of an intruder;
• wherein the alarm means includes means for increasing the current drawn by the receiving unit from the cable conductors to provide the alarm signal;
• and
• wherein the alarm means includes a light and means responsive to the alarm signal for connecting the light across the cable to illuminate the light and increase the current drawn by the receiving unit from the cable.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the AC signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• demodulating means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presence of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm means, including an indicator operable to increase the current drawn from said cable, responsive to the detecting means output signal for operating said indicator and applying said increased current as said alarm signal to the cable for remotely indicating the detection of an intruder;
• a transformer having two primary windings and a secondary winding;
• a capacitor connected in series between one terminal of opposite polarity of each primary winding;
• the second terminals of each primary winding being respectively connected to the two conductors of the cable;
• the DC power for the receiving unit being taken from across the capacitor;
• and
• means connected to the transformer secondary winding for providing the reference signal.

For use with an intrusion alarm system of the type having a control unit, a plurality of transmitting units for transmitting a signal into a protected area, and a plurality of receiving units for receiving signals from the protected area and detecting components in the received signals representative of an intruder, the control unit, transmitting units, and receiving units all being interconnected by a cable having two conductors, over which two conductors the control unit sends DC power and an AC signal to the receiving units, and over which two conductors the receiving units send an alarm signal back to the control unit indicating the detection of an intruder, a receiving unit comprising:

• connecting means connected to the cable and responsive to the AC and DC signals on the cable for providing DC power to the receiving unit and a reference signal having a frequency equal to that of the AC signal on the cable;
• a receiving transducer for receiving signals from the protected area and for providing an electrical output signal representative of the received signals;
• demodulating means responsive to the transducer output signal and to the reference signal for demodulating the transducer output signal to provide an output signal;
• detecting means responsive to the demodulating means output signal for detecting the presence of doppler shifted echoes resulting from intruder movement in the protected area and for producing an output signal representative thereof;
• and
• alarm means, including an indicator operable to increase the current drawn from said cable, responsive to the detecting means output signal for operating said indicator and applying said increased current as said alarm signal to the cable for remotely indicating the detection of an intruder;
• wherein the signal transmitted by the transmitting units is modulated at the modulation frequency lower than the frequency of the AC signal, and wherein the detection means further includes:
• filter means responsive to signals having a component at the modulation frequency for providing an output signal;
• and
• means for applying the demodulating means output signal to the filter means.