US3781859A - Controlled wave pattern ultrasonic burglar alarm - Google Patents

United States Patent [1 1 Hermans Dec. 25, 1973 [54] CONTROLLED WAVE PATTERN 3,638,210 1/1972 Hankins et al 340/258 A ULTRASONIC BURGLAR ALARM 3,629,812 12/1971 Amato 3,582,870 6/l97l Peterson et al 340/258 A [76] Inventor: Albert L. Hermans, c/o Seabroad Elecmc, Bancroft -l San Primary Examiner-John w. Caldwell Leandro, Callf- 94577 Assistant Examiner-Glen R. Swann, III [22] Filed; APR 19, 1972 Attorney-Harris Zimmerman I A'burglar alarm employs ultrasonic sound to protect a [52] U.S. CI. 340/258 A, 343/7.7 plurality of rooms. Each protected room contains a [51] Int. Cl.

G08b

13/16 transmitter which emits an ultrasonic signal in a con- [58] Field ol' Search 340/258 A, 1 R; trolled wave pattern. The signal is received, filtered,

UNITED STATES PATENTS alarm is given 3,733,580 5/1973 Beeken 340/1

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8 Claims, 7 Drawing Figures IRECEIVERI I RECEIVER I I

RECEIVER

5 I I Fuecou uzfl IDECOUPLERI IIDECOUPLERI a I J J I RADIO /8 9 ELECTRICAL LIGHTNING FREQUENCY NOISE

FILTER FILTER FILTER

7 SENSITIVITY /IO '2 l3 CONTROL AMPLIFIER l6 PHASE BAND PASS TURBULENCE AMPL'F'ER DETECTOR AMPLIFIER CIRCUIT SUPPLY 05C. I I I8 CIRCUIT l9 MEMORY TRANSMITTER TRANSMITTER I LOG'C OUTPUT OLJTSUT WALK TEST ITRANSMITTER I ITRANSMITTERJ 'f 'I RELAY LRECEIVER RECEIVER RECEIVER /5 I I I DECOUPLER DECOUPLER DECOUPLER 6 I I I ELECTRICAL RADIQ LIGHTNING FREQUENCY NOISE FILTER FILTER FILTER SENSITIVITY CONTROL AMPLIFIER I2 |3 |4 I6 A

HASE

8 ND PASS TURBULENCE I AMPL'F'ER DETECTOR AMPLIFIER CIRCUIT |5\ INTRUDER SUPPLY '8 I9 MEMORY TRANSMITTER TRANSMITTER I LOGIC OUTPUT OUTPUT F M l 2 WALK TEST ALARM l7 TRANsMITTER TRANsMITTER CIRCUIT

RELAY

1 CONTROLLED WAVE iPATTERN ULTRASONIC BURGLAR ALARM BACKGROUND OF THE INVENTION case of ultrasonic alarms, to random background noise such as jet planes, auto traffic, etc., and to nonintrusive movement, such as air turbulence, hanging decorations, draperies and the like.

DESCRIPTION OF THE PREFERRED EMBODIMENT The alarm system, shown in block diagram in FIG. 1, is powered by a regulated

power supply

1, which includes a standby battery to provide power during a blackout and to defeat any attempt to unplug the system. The

oscillator

2 generates an ultrasonic tone, at approximately 20,000 Hz, which is fed to the transmitting

transducers

3 which are installed in the areas to be protected. The oscillator signal is sampled by the fail

safe circuit

4, which is connected to the

alarm circuit relay

17. If the

oscillator

2 should fail to operate, either through malfunction or an attempt to disrupt the system, the fail-

safe circuit

4 will sense the diminished output of the

oscillator

2, and will actuate the

alarm circuit relay

17. The oscillator signal is also sampled by the

phase detector

13.

Mounted in each protected area in association with each transmitting

transducer

3 are the

receiving transducers

5, connected to the system by

high impedance decouplers

6. The

receivers

5 receive the ultrasonic signal emitted by the

transducers

3, and the received signal is passed through the

decoupler

6 to the noise filters. The electrical noise filter 7, the

radio frequency filter

8, and the lightning filter ]remove extraneous noise which could cause a false alarm. The filtered signal then goes to the

amplifier

10, and the

sensitivity control

1 1. The sensitivity is adjusted to pass the maxi mum signal strength without causing a false alarm. The signal then goes to the

amplifier

12, and the

phase detector

13. The phase detector mixes the received signal with the sampled signal from the

oscillator

2, and produces a doppler signal which is amplified by the

band pass amplifier

14, which senses and amplifies a frequency component of approximately 35 Hz, produced by that of an intruder moving within the protected areas. The amplified doppler signal is then fed through the

turbulence circuit

16 to the

intruder circuit

15 which sends an alarm signal to the

alarm circuit relay

17. The alarm signal is delayed, however, by the

memory logic circuit

18, which receives the signal through the normally closed

walk test switch

19. The

memory logic

18 delays the alarm signal once for a short time, approximately one second, to provide a further safeguard against false alarms. The delay does not reset for a period of time, approximately one minute, so that a slow stepping burglar will still actuate the alarm. After the time delay, the alarm signal actuates the

alarm relay

17 which operates an automatic police call, siren or other alarm device desired.

The schematic diagram of FIG. 3 shows the limiter amplifier and the level amplifier circuit that makes up the

turbulence circuit

16, and the

intruder circuit

15 of FIG. 1.

Amplfier

26 receives the doppler signal through

conductor

27, and puts out an amplified signal through

conductor

28.

Line

29 provides positive operating voltage,

line

30 provides negative operating voltage, and

line

31 is ground. Connected from

line

27 to

line

28 is a

diode bridge

32 in a feedback arrangement. There are four series diodes in one direction in parallel with four diodes in the reverse direction. Each

diode

33 has a forward breakdown voltage of 0.6 volts, so that the feedback effect takes place whenever the doppler signal is greater than i 2.4 volts. Thus all booming sounds picked up by the

receivers

5 are limited in amplitude so that the large signals cannot blast their way through to the

intruder circuit

15. The signal is then conducted by

line

28 to the parallel back to

back diodes

34.

Again each diode has a forward breakdown voltage of 0.6 volts. Thus the first 0.6 volts of the doppler signal excursion in either the positive or negative direction is clipped eliminating the low voltage component of the doppler signal which results from random background noise. The signal then goes through the limiting

resistor

35 and the

coupling capacitor

36, to the

half wave rectifier

37. The

rectifier

37 conducts the negative portion of the doppler signal to ground, and the remaining signal, lying between 0.6 volts and 2.4 volts, then passes through

resistor

41 to

conductor

42 and to the amplitier 48 which is part of the

intruder circuit

15. A threshold level is formed by

resistor

43 and

diode

44 at

conductor

49. When the DC. level at

conductor

42 exceeds the set level at

conductor

49,

amplifier

48 passes the signal to

conductor

50 which is considered an alarm condition. The positive voltage for

amplifier

48 is provided at

line

45, negative voltage at 46 and ground at 47.

The circuits shown in FIG. 4 are the memory logic l8 and

walk test

19 as shown in FIG. ll. It consists of

transistor

53 biased normally off and

transistor

54 biased normally on.

Transistor

53 receives the alarm actuating signal from the fail

safe circuit

4 or from the

intruder circuit

15 through balancing

resistor

52. When an alarm signal comes from

intruder circuit

15 through

conductor

50 of FIG. 3, it enters through

resistor

52 of FIG. 4 to the base of

transistor

53 which causes it to conduct. The bias voltage from

resistor

55 which normally holds

transistor

54 in the conducting condition is removed and

transistor

54 stops conducting.

Resistor

56 and

resistor

61 in series with

relay

62 are current limiting devices. When

transistor

54 ceases to conduct, the voltage normally holding

relay

62 engaged disappears and an alarm condition exists. However, after system has been set in the non-alarm condition for a period of 60 seconds current flowing through the conducting

transistor

54 flows through

resistor

56 to

conductor

60 and through

resistor

58 which charges

capacitor

57 to full charge. When

transistor

54 ceases to conduct, the current stored in

capacitor

57 flows through

diode

59 to

conductor

60 through

resistor

61 and holds

relay

62 engaged for a period of approximately 1 secend.

The

resistor

63 in parallel with

capacitor

57 is selected at random and changes the discharge time and charge time of the memory logic circuit so that no one will know the actual time delay of the circuit. The wall

test jack switch

19 used during installation, opened by plugging in an installers walk test device, opens the circuit at

capacitor

57 from the circuit so that the relay will respond instantly when

transistor

54 switches off.

The circuitry of FIG. 5 shows a schematic view of a

receiver transducer

5 connected to the central alarm system. The

receiver

5 consists of a tuned

metal plate

64, which is tuned to the ultra sonic frequency at which the system operates. The plate receives this frequency from

transmitter

3. A

piezoelectric crystal

65, which is connected to the secondary winding 66 of the

transformer

67, converts the received sound to electrical signals. The

transformer

67 adjusts the reaction of the receiver circuit to provide optimum sensitivity at the operating frequency. The gain of the signal induced in the primary winding 68 is controlled by the

variable resistor

69, which is a precision turn potentiometer. The signal then goes through

terminal block

70 to the decoupling capacitors 7H. Conductors 72 connect to the two other decoupler inputs.

Isolation transformer

73 isolates the three decoupler inputs from the electronics of the control unit and also works with the electrical noise filter circuit.

7 the controlled wave pattern system is much more sensi FIG. 2 shows a typical installation of a transmitting

transducer

20 and a receiving

transducer

21 in a

small room

22, and the controlled

wave pattern

23 that is used to detect intrusion. Both

transducers

20 and 21 are directional, and are mounted on the

ceiling

24 of the

room

22 with their sensitive axes towards the floor. The

transmitter

20 directs a wide beam of sound toward the floor, and that beam is reflected and rereflected many times before being received by the

receiver

21. It can be seen that there is no line of sight communication path between the

transducers

20 and 21.

Therefore decorations hanging from the ceiling and tall decorative plants moving in convection currents will not actuate the alarms. This is due to the fact that tive to sustained movement through the multireflected beam than to short movements directly between the

transducers

20 and 21.

It should be noted that because of the low profile of the sound emitting tuned plate, the

receiver

5 or

transmitter

3 are not readily effected by air currents blowing against them. Also, with slight modification they can be flush mounted in any wall or ceiling, permitting an unobstructive and effective installation.

FIGS. 6 and 7 are views of

receiver

5. The

receiver

5 consists of a long

rectangular metal box

74, with a

cover

75 held on by

screws

76 which fit through

slots

77 of the

box

74. The

cover

75 has double-sided foam

adhesive tape

78 applied to it, to facilitate easy installation to any smooth surface. In one corner of the

box

74 is a small

rectangular plastic box

79 in which the

potentiometer

69 and the

transformer

67 are imbedded in epoxy plastic. The

hole

85 allows adjustment of the

potentiometer

69 without removal of the

cover

74.

The

tuned plate

64 is attached to the

box

74 by

bolts

81, which extend through the bottom 80 of the box. The

plate

64 is spaced apart from the

box

74 by

bushings

82. The

crystal

65 is soldered and cemented to the tuned

plate

64, to provide good electrical and mechanical union. The

crystal

65 converts the vibrations of said

plate

64 into electrical signals, as discussed above.

The

transmitters

3 have the same outward appearance as the

receivers

5. Each transmitter is housed in a box of the same dimensions as the

box

74, and each employs the same tuned

plate

64

piezoelectric crystal

65 combination to emit the ultrasonic signal, the

crystal

65 vibrating said tuned

plate

64 to oscillate at the correct ultrasonic frequency. The

transmitters

3, however, are not adjustable.

It should be noted that because of the low profile of the

box

74, the

receiver

5 or

transmitter

3 are not readily affected by air currents blowing against them. Also, with slight modification they can be flush mounted, in any wall or ceiling, permitting an unobstructive and effective installation.

It should also be noted that there is ample room in the

box

74 for a thermal switch, and therefore the

box

74 could also house a fire sensor for a fire alarm system operated in conjunction with the present burglar alarm system.

I 2.. A burglar alarm system according to

claim

1, wherein said turbulence circuit means consists of an integrated circuit amplifier which receives said doppler signal as an input, and whose output is connected to a clipping circuit to remove background noise, said clipping circuit consisting of two parallel diodes of predetermined forward breakdown voltage, each aligned in a conductive direction opposite the other, the output of said clipping circuit being connected in series to a series combination of a resistor, a filter capacitor, and a half-wave rectifier, the output of said half-wave rectifier being connected to said intrusion detection means; said turbulence circuit further including a feedback circuit to remove voltage peaks connected between said input and said output of said integrated circuit amplifier, said feedback circuit consisting of a plurality of diodes of predetermined forward breakdown voltage, a first number of said plurality of diodes connected in series in the same conductive direction, the remainder of said plurality of diodes connected in series and arranged in parallel connection with said first number of diodes, said remainder of diodes aligned in conductive direction opposite to said first number of diodes.

3,. A burglar alarm system according to

claim

1, wherein said decoupler means comprises capacitive impedance means, connected between said receiver means and said filter means, to increase the voltages of said electrical signal.

5. The burglar alarm system according to

claim

4, wherein said walk test switch is connected between said second terminal of said capacitor and ground, to selectively remove said capacitor from said timing circuit, thereby causing any alarm to be controllably rendered instantly.

6. The burglar alarm system according to

claim

5, wherein said receiver means comprises a plurality of ultrasonic receivers, each of said receivers containing a metal plate, each said plate having a resonant frequency equal to said predetermined frequency at which said transmitter means emits said ultrasonic sound.

7. The burglar alarm system according to

claim

6, further including a piezoelectric crystal affixed to each said metal plate to convert the vibrations of each said plate to an electrical signal, each said crystal being connected in parallel with the primary winding of a variable transformer, the secondary winding of each said transformer being connected in parallel with a variable potentiometer for adjusting the sensitivity of each said receiver.

1. A burglar alarm system for detecting intrusion into a protected enclosure comprising: oscillator means to generate an ultrasonic signal of predetermined frequency; a directional, wide-beam transmitter means, connected to said oscillator means and located inside said protected enclosure with its transmitting axis directed toward the floor of said enclosure, to emit an ultrasonic sound at said predetermined frequency in a beam toward said floor; directional receiver means, located inside said protected enclosure, with its sensitive axis directed toward said floor of said enclosure to receive and convert said ultrasonic sound to an electrical signal, the communication path between said transmitter means and said receiver means being other than the line of sight, such that said sound emitted from said transmitter means must be reflected a plurality of times between said floor and the ceiling of said enclosure before it can be received by said receiver means; decoupler means, connected to said receiver means, to present an input impedance to said electrical signal; filter means, connected to said decoupler means, to filter extraneous electrical noise from said electrical signal; phase detector means, connected to said filter means and said oscillator means, to mix said electrical signal and said ultrasonic signal, and to generate a doppler signal from the phase difference between said electrical signal and said ultrasonic signal; intrusion detection means, connectEd to said phase detector means, to generate an alarm actuating signal upon reception of a doppler signal of predetermined frequency and amplitude indicative of human movement inside the protected enclosure; alarm means, connected to said intrusion detection means, to render an alarm upon receipt of said alarm actuating signal; fail safe means, connected to said oscillator means and said alarm means, to generate an alarm actuating signal upon failure of said oscillator means to generate said ultrasonic signal of predetermined frequency; turbulence circuit means connected to said phase detection means and said intrusion detection means to remove from said doppler signal electrical noise due to random noise and air turbulence in said protected enclosure; memory logic means to delay rendering of said alarm; and a walk test switch causing any alarm to be controllably rendered instantly, so that installation and adjustment of said system is facilitated.

2. A burglar alarm system according to claim 1, wherein said turbulence circuit means consists of an integrated circuit amplifier which receives said doppler signal as an input, and whose output is connected to a clipping circuit to remove background noise, said clipping circuit consisting of two parallel diodes of predetermined forward breakdown voltage, each aligned in a conductive direction opposite the other, the output of said clipping circuit being connected in series to a series combination of a resistor, a filter capacitor, and a half-wave rectifier, the output of said half-wave rectifier being connected to said intrusion detection means; said turbulence circuit further including a feedback circuit to remove voltage peaks connected between said input and said output of said integrated circuit amplifier, said feedback circuit consisting of a plurality of diodes of predetermined forward breakdown voltage, a first number of said plurality of diodes connected in series in the same conductive direction, the remainder of said plurality of diodes connected in series and arranged in parallel connection with said first number of diodes, said remainder of diodes aligned in conductive direction opposite to said first number of diodes.

3. A burglar alarm system according to claim 1, wherein said decoupler means comprises capacitive impedance means, connected between said receiver means and said filter means, to increase the voltages of said electrical signal.

4. A burglar alarm system according to claim 3, wherein said memory logic means comprises a first transistor normally biased in the off condition, with a base connection to said intrusion detection means, and switchable to the on condition when said base connection receives said alarm actuation signal; a second transistor normally biased in the on condition, with a base connection to the collector of said first transistor and switchable to the off condition when said first transistor switches to the on condition, the emitter of said second transistor being connected in series with the first terminal of the operating coil of an alarm relay, the second terminal of said operating coil being connected to ground; a diode connected in parallel relationship with said operating coil to protect said second transistor from the inductive surge of said operating coil; and a timing circuit comprising a charging resistor connected to a first terminal of a capacitor, the second terminal of said capacitor being connected to ground, said timing circuit being connected to said emitter of said second transistor in parallel relationship with said operating coil, and a second resistor connected to said first terminal of said capacitor and to ground, whereby reception of an alarm actuating signal will turn on said first transistor, causing said second transistor to turn off, and causing said capacitor to discharge, through said charging resistor, to a voltage insufficient to operate said operating coil of said alarm relay, thereby rendering a delayed alarm.

5. The Burglar alarm system according to claim 4, wherein said walk test switch is connected between said second terminal of said capacitor and ground, to selectively remove said capacitor from said timing circuit, thereby causing any alarm to be controllably rendered instantly.

6. The burglar alarm system according to claim 5, wherein said receiver means comprises a plurality of ultrasonic receivers, each of said receivers containing a metal plate, each said plate having a resonant frequency equal to said predetermined frequency at which said transmitter means emits said ultrasonic sound.

7. The burglar alarm system according to claim 6, further including a piezoelectric crystal affixed to each said metal plate to convert the vibrations of each said plate to an electrical signal, each said crystal being connected in parallel with the primary winding of a variable transformer, the secondary winding of each said transformer being connected in parallel with a variable potentiometer for adjusting the sensitivity of each said receiver.

8. The burglar alarm system of claim 5 wherein said transmitter means comprises at least one ultrasonic transmitter containing a metal plate having a resonant frequency equal to the predetermined frequency at which said transmitter means emits ultrasonic sound, and a piezoelectric crystal, affixed to said plate, which receives said ultrasonic signal from said oscillator means to vibrate said plate at said resonant frequency.