GB2040142A

GB2040142A - Transponder type burglar alarm operated by vibration

Info

Publication number: GB2040142A
Application number: GB7944604A
Authority: GB
Original assignee: New Japan Radio Co Ltd
Current assignee: New Japan Radio Co Ltd
Priority date: 1978-12-31
Filing date: 1979-12-31
Publication date: 1980-08-20
Also published as: GB2040142B; FR2445566B1; JPS55112582A; FR2445566A1

Abstract

A radio alarm system generally comprises a transmitter, 12, a receiver, 14, and/or a combined transmitter and receiver 10, and a wireless detecting means 20 including no power supply. The transmitter is located at one area of a structure for continuously transmitting a radio signal to establish an electromagnetic field therethrough. The wireless detecting means 20 comprises a receiving unit 30, a detecting unit 40 including a detecting element 44 connected in parallel with a normally closed vibration switch 46, and a transmitting unit 50. Upon the occurrence of vibrations exceeding a predetermined intensity, the normally closed vibration switch 46 is caused to open, producing a voltage across the detecting element 44, which voltage is impressed on to the original potential and resonated through a resonant circuit 52, 54, 56, through which a frequency multiplied warning signal is transmitted to the receiver to trigger an alarm device. <IMAGE>

Description

SPECIFICATION Radio alarm system This invention relates to a radio alarm system, and more particularly to a novel and highly-improved radio alarm system which comprises a transmitter, a receiver and/or a combined transmitter and receiver, and a wireless detecting means.

Various detectors are known and are used for burglar detection and alarms. In the conventional alarm system, vibration detectors are typically mounted on windows, doors or walls of a structure to be protected, and these detectors are coupled to electric wires which are further connected through a private telephone line to a guard station.

Such an alarm system needs troublesome wiring such as makes the circuit complicated.

To overcome this shortcoming, an intrusion detection system comprising a radio transmitter, a receiver and a detector has been proposed. A major drawback to this proposal is that each detector requires both a power supply and wiring, and this system is typically prone to produce a false alarm after installation or the actual alarm condition may not be sensed at greater expense and disappointment. Furthermore, this system requires periodic maintenance an exhausted cell must be exchanged for a new one, so that the system is complex and expensive to install and maintain.

An object of the present invention is to provide a simplified construction of a radio alarm system which comprises a transmitter disposed at one area of a structure, a wireless detecting means mounted on the surface to be protected and a receiver disposed at another area or at the same location as the transmitter.

A further object of the present invention is a provision of a radio alarm system which can be made small and easy to install, and is maintained atrela- tively low cost.

According to the invention, there is provided a radio alarm system for detecting and indicating the vibrations caused by burglarious attack, said system comprising: a transmitter disposed at one area of or near a structure to be protected for continously transmit- ting a radio wave of frequency F1 around the protected structure, a wireless detecting means including no power supply and secured to a part of the structure for receiving the radio wave signal Fl, said wireless detecting means creating a resonance potential and transmitting a radio wave of different frequency F2 upon detection of vibrations exceeding a predetermined intensity, and a receiver disposed at one area of or near the structure and arranged to trigger an alarm device upon detection of the radio wave of frequency F2.

An embodiment of the invention is hereinafter described, by way of example only, with reference to the accompanying drawing, wherein: Fig. 1 is a front elevation of a radio alarm system of the present invention in use on a window pane; Fig. 2 is a front elevation of another embodiment of the present invention; Fig. 3 is a diagram of a wireless detecting means used in the present invention; and Fig. 4 is a schematic diagram of a practical embodiment of the wireless detecting means.

The radio alarm system of the present invention generally comprises a transmitter, a receiver and/or a combined transmitter and receiver and a wireless detecting means including no power supply therein.

A transmitter 12 and a receiver 14 are either made into independent units or into a combined transmitter and receiver 10. Referring to Figures 1 and 2, the transmitter 12 and the receiver 14 and/or the combined transmitter and receiver 10 are usually located at one area of or near a structure to be protected. A radio wave of a frequency F, is continuously trans mittedfrom an antenna 13 of the transmitter 12 toward or around the structure.

A wireless detecting means 20 is usually secured to the surface of the structure to pick up vibration, and in the drawings, it is rigidly secured to a surface of a glass pane indicated at 16.

As shown in Fig. 3, the wireless detecting means 20 generally comprises a circuit 22 connected in series with a detecting element 24 such as diode and a normally closed vibration switch 26 connected in parallel with the detecting element. The switch 26 consists of a contact 26a and a contact point 26b, which are designed to engage or disengage with each other by vibration. Alternatively, the switch may be a normally open type arranged to close by vibration. Suitable switches are a magnetic switch, a vibration switch and so on, which are physically but not electrically actuated to open or close by vibration caused by burglarious attack.

The radio wave of frequency F1 from the antenna 13 is received by an antenna 15 of the receiver 14, and it flows through the circuit 22, and most of the current energy is used up in heat. Thus, a radar warning net is established between the transmitter and the wireless detecting means.

Upon the occurrence of vibration resulting from an attempt to breakthrough the protected surface, the contact 26a will be caused to disengage physically from the contact point 26b, thus inducing voltage across the detecting element 24 of the wireless detecting means 20. Then, a radio wave of a frequency F2 is transmitted back from the detecting means 20 toward the antenna 15 of the receiver 14 to induce a resonance potential through the receiver, thus triggering an alarm device (not shown).

In Fig. 4, a schematic diagram of a practical embodiment of the wireless detecting means is shown. In the drawing, the wireless detecting means 20 generally comprises a receiving unit 30, a detecting unit 40 and a transmitting unit 50.

The receiving unit 30 comprises a circuit 32 including a variable capacitor 34 connected in parallel with an inductor 36, and an antenna 38 connected into the circuit 32. The detecting unit 40 comprises a circuit 42 connected in series with a detecting element 44 such as a diode and a normally closed vibration switch 46 connected in parallel with the detecting element. The closed vibration switch 46 consists of a contact 46a and a contact point 46b which are designed to disengage by vibration caused by burglarious attack on the structure.

The transmitting unit 50 comprises a capacitor 52, a resistor 54 and a pair of variable inductors 56 to form a resonant circuit.

In use, one or more wireless detecting means 20 are rigidly secured by screws or adhesive on one or more surfaces to be protected at a plurality of spaced-apart locations to detect vibration thereof.

The radio wave of frequency F1 is continuously transmitted toward or around the structure to be protected to form a radar warning net between the transmitter 10 and the wireless detecting means 20, and the radio wave is normally received by the wireless detecting means 20, through which resonance current flows and goes into heat.

When shock or vibration is caused by a burglarious attack, the contact 46a is forced to disengage physically from the contact point 46b and to induce voltage across the detecting element 44. The induced voltage is impressed to the original potential through the circuit 42 and subsequently resonated through the resonant circuit including the capacitor 52, the resistor 54 and the inductors 56, and a radio wave signal of multiplied resonance frequency F2 is transmitted from the antenna 58 back to the antenna 13 of the receiver 14, thus triggering an alarm device (not shown).

As fully explained in the foregoing paragraphs, there are provided a transmitter, a receiver and/or a combined transmitter and receiver disposed at one area for continuously transmitting a radio wave signal F1 around a warning zone of a structure to be protected, and one or more wireless detecting means are disposed on such structures as window and door frames, glass panels, walls and soon, thus establishing a radar warning net between the transmitter and the wireless detecting means. A physically actuated or no-voltage vibration switch is connected in parallel with the detecting element of the wireless detecting means. The radio wave which is continuously transmitted from the transmitter is received by the wireless detecting means, through which current flows and goes into heat.

Should the window be broken or a strong vibration exceeding a predetermined intensity be given, the normally closed vibration switch will open physicallyto produce an alarm signal of a multiplied resonance frequency F2 greater than the original resonance frequency F1 emitted from the transmitter 10. The multiplied resonance frequency F2 is received by the receiver 14 in order to trigger an alarm device.

Claims

1. A radio alarm system for detecting and indicating the vibrations caused by burglarious attack, said system comprising: a transmitter disposed at one area of or near a structure to be protected for continuously transmitting a radio wave of frequency F, around the protected structure; a wireless detecting means including no power supply and secured to a part of the structure for receiving the radio wave signal F1, said wireless detecting means creating a resonance potential and transmitting a radio wave of dif ferentfrequency F2 upon detection of vibrations exceeding a predetermined intensity, and a receiver disposed at one area of or near the structure and arranged to trigger an alarm device upon de9ction of the radio wave of frequency F2.

2. A radio alarm system as claimed in claim 1 ccmprising a combined transmitter and receiver disposed at one area of or near the structure to be protected for continuously transmitting the radio wave of frequency F, around the protected structure, thus establishing a radio warning net between said combined transmitter and receiver and the structure, said wireless detecting means being rigidly secured to a solid surface of a structure for receiving the radio wave signal F, and being arranged to create a resonance potential and transmit a radio wave of multiplied resonance frequency F2 when shocked or broken.

3. A radio alarm system as claimed in claim 1 or2 wherein said wireless detecting means comprises a receiving unit, a detecting unit and a transmitting unit.

4. A radio alarm system as claimed in claim 3 wherein said receiving unit comprises a circuit including a variable capacitor connected in parallel with an inductor, and an antenna connected into the circuit, said detecting unit comprises a detecting element such as a diode and a normally closed switch connected in parallel with the detecting ele ment, and said transmitting unit comprises a reson ant circuit including a capacitor, a resistor and a pair of variable inductors.

5. A radio alarm system as claimed in any pre ceding claim comprising a transmitter and a receiver and/or a combined transmitter and receiver, and a plurality of wireless detecting means.

6. A radio alarm system substantially as hereinbefore described with reference to the accom panying drawing.