GB1602112A - Alarm equipment - Google Patents

Description

(54) ALARM EQUIPMENT (71) We, RCA SECURITY SYSTEMS LIMITED, a British Company of Lincoln Way, Windmill Road, Sunbury-on-Thames, Middlesex, England do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to alarm equipment, and one object is to provide a signal at a detector in response to a symptom of an intrusion into an area, for example the breaking of a window which may be due to an intruder.

According to a first aspect of the present invention there is provided alarm equipment, to signal a symptom of an intrusion into an area, including an optical fibre, a source of light at one end of the fibre, and a detector of light at the other end and means arranged to break, deform or displace the fibre, and thereby modify the transmission of light from the source to the detector along the fibre in response to an alarm condition, said means comprising a window or wall member which forms part of the boundary of the area to be protected and which has the optical fibre incorporated therewith, the member being arranged to break or distort in response to said intrusion symptom, and thereon to thus affect the fibre.

According to a second aspect, the present invention provides alarm equipment, to signal symptoms of intrusion in to an area, including an optical fibre arranged to be broken or deformed in response to the penetration of a wall, whereby the transmissibility of light in the optical fibre is altered, and means to indicate an alteration in the transmission of light in the fibre.

An optical fibre is an elongate filament of transparent or possibly translucent material, for example glass or a polymer which is flexible to be capable of following an irregular path from one end to the other, and which can transmit light from one end face to the other end face with substantially uniform attenuation however much the fibre is bent. The cross sectional area of the fibre can vary from that of a very fine thread to possibly a rod of perhaps 1/4 inch in diameter and in some applications an optical cord may consist of a number of fibres bundled together extending side by side. A filament usually comprises a core of one material surrounded by a sleeve of another with a different refractive index so that light is reflected at the interface where the two materials are in intimate contact and travels along the fibre with little attenuation.

A glass fibre can transmit light with little loss for a considerable distance, and a plastics fibre can transmit light with little loss over perhaps 5 or 10 feet.

The source of light at one end may be a light-emitting diode producing an amout of light dependent upon an exciting electrical signal and the detector may consist of a photo-electric detector for giving an electrical signal dependent upon the amount of light experienced by its light sensitive surface. The source may be modulated so that if the fibre is broken or damaged, light similar to that from the source will not be easily introduced deliberately or accidentally at the break.

Thus, if the equipment is to detect symptoms of an intrusion, it might be arranged that the fibre is secured around the edge of a window so that if the window is cracked or broken the fibre will be broken or deformed or a section of it may be displaced in such a way that the attenuation of light along the fibre will be increased, and the detected signal will in consequence disappear or be reduced so that an alarm can be given. The fibre might be arranged to be broken, or deformed in response to the penetration of a wall in a similar manner.

If the equipment would give an alarm if a fire starts, and if a part of said fibre may be exposed to heat in the area to be protected, the consequent rising temperature when a fire starts can cause the material of the fibre to flow or melt and again that will change the attenuation.

The alarms described above depend upon some kind of physical deformation, and preferably severing of the fibre if an alarm is to be detected.

The invention may be carried into practice in various ways, and certain embodiments will now be briefly described by way of example with reference to the accompanying drawings, which are sketches of various ways of changing the attenuation of light along an optical fibre.

Figure 1 shows a window 11 in a frame 12 and an optical fibre 13 arranged around its edge and attached to it by an epoxy resin or other transparent adhesive which also protects the fibre during cleaning of the window, There is a light source 14 mounted in the frame, and a light detector 15 also mounted in the frame, each being a respective end of the fibre.

If the glass is cracked or broken as indicated at 16 the fibre will also be broken so that the signal received at 15 from the light at 14 will be lost and an alarm can be given' In Figure 2 an alternative which does not embody the invention, but is described as background, two adjacent sections 26 and 27 of an optical fibre can have their opposed faces in line or out of line as shown in the figure by operation of a servo mechanism 28 possibly operated electro-magnetically from an alarm voltage from a conventional detector and applied to terminals 29. If the detector detects and alarm and operates the actuator 28, the fibre part 27 will be moved to the position shown in Figure 2, and immediately the attenuation along the fibre will be increased substantially.

A similar actuator although not conforming with the invention, could be used as shown in Figure 3, to move a linking section 31 of optical fibre from a position in line with the adjacent sections 26 and 27 or as shown in Figure 4 to move a shutter 32 from a position in which an aperture permits light to flow from one section 26 to the other or prevents such flow of light. The figures are diagrammatic and in general the opposed fibre ends will be in intimate contact with each other in the lighttransmitting position.

The source of light 14 can be modulated regularly or recognisable pattern so that a burglar could not easily apply the correct light to a broken end of fibre where he had made an entry.

WHAT WE CLAIM IS: 1. Alarm equipment, to signal a symptom of an intrusion into an area, including an optical fibre, a source of light at one end of the fibre, and a detector of light at the other end and means arranged to break, deform or displace the fibre, and thereby modify the transmission of light from the source to the detector along the fibre in response to an alarm condition, said means comprising a window or wall member which forms part of the boundary of the area to be protected and which has the optical fibre incorporated therewith, the member being arranged to break or distort in response to said intrusion symptom, and thereon to thus affect the fibre.

2. Alarm equipment as claimed in Claim 1 in which the fibre comprises a core of one material surrounded by a sleeve of another material with a different refractive index.

3. Alarm equipment as claimed in either of the preceding claims in which the optical fibre is of glass.

4. Alarm equipment as claimed in Claim I or Claim 2 in which the optical fibre is of plastics material.

5. Alarm equipment as claimed in any of the preceding claims including means for regularly modulating the source of light.

6. Alarm equipment as claimed in any of Claims 1--4 including means for modulating the light in a recognizable pattern.

7. Alarm equipment as claimed in any of the preceding claims in which the fibre is secured around the edge of a glass window.

8. Alarm equipment as claimed in any of Claims 1--6 in which the fibre is positioned to be broken or deformed in response to the penetration of a wall.

9. Alarm equipment, to signal symptoms of intrusion into an area, including an optical fibre arranged to be broken or deformed in response to the penetration of a wall, whereby the transmissibility of light in the optical fibre is altered, and means to indicate an alteration in the transmission of light in the fibre.

10. Alarm equipment as claimed in Claim 9 comprising a source of light modulated in a recognizable pattern at one end of the optical fibre.

I 1. Alarm equipment including an optical fibre constructed and arranged substantially as herein specifically described with reference to figure 1 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. to flow or melt and again that will change the attenuation. The alarms described above depend upon some kind of physical deformation, and preferably severing of the fibre if an alarm is to be detected. The invention may be carried into practice in various ways, and certain embodiments will now be briefly described by way of example with reference to the accompanying drawings, which are sketches of various ways of changing the attenuation of light along an optical fibre. Figure 1 shows a window 11 in a frame 12 and an optical fibre 13 arranged around its edge and attached to it by an epoxy resin or other transparent adhesive which also protects the fibre during cleaning of the window, There is a light source 14 mounted in the frame, and a light detector 15 also mounted in the frame, each being a respective end of the fibre. If the glass is cracked or broken as indicated at 16 the fibre will also be broken so that the signal received at 15 from the light at 14 will be lost and an alarm can be given' In Figure 2 an alternative which does not embody the invention, but is described as background, two adjacent sections 26 and 27 of an optical fibre can have their opposed faces in line or out of line as shown in the figure by operation of a servo mechanism 28 possibly operated electro-magnetically from an alarm voltage from a conventional detector and applied to terminals 29. If the detector detects and alarm and operates the actuator 28, the fibre part 27 will be moved to the position shown in Figure 2, and immediately the attenuation along the fibre will be increased substantially. A similar actuator although not conforming with the invention, could be used as shown in Figure 3, to move a linking section 31 of optical fibre from a position in line with the adjacent sections 26 and 27 or as shown in Figure 4 to move a shutter 32 from a position in which an aperture permits light to flow from one section 26 to the other or prevents such flow of light. The figures are diagrammatic and in general the opposed fibre ends will be in intimate contact with each other in the lighttransmitting position. The source of light 14 can be modulated regularly or recognisable pattern so that a burglar could not easily apply the correct light to a broken end of fibre where he had made an entry. WHAT WE CLAIM IS:

1. Alarm equipment, to signal a symptom of an intrusion into an area, including an optical fibre, a source of light at one end of the fibre, and a detector of light at the other end and means arranged to break, deform or displace the fibre, and thereby modify the transmission of light from the source to the detector along the fibre in response to an alarm condition, said means comprising a window or wall member which forms part of the boundary of the area to be protected and which has the optical fibre incorporated therewith, the member being arranged to break or distort in response to said intrusion symptom, and thereon to thus affect the fibre.

2. Alarm equipment as claimed in Claim 1 in which the fibre comprises a core of one material surrounded by a sleeve of another material with a different refractive index.

3. Alarm equipment as claimed in either of the preceding claims in which the optical fibre is of glass.

4. Alarm equipment as claimed in Claim I or Claim 2 in which the optical fibre is of plastics material.

5. Alarm equipment as claimed in any of the preceding claims including means for regularly modulating the source of light.

6. Alarm equipment as claimed in any of Claims 1--4 including means for modulating the light in a recognizable pattern.

7. Alarm equipment as claimed in any of the preceding claims in which the fibre is secured around the edge of a glass window.

8. Alarm equipment as claimed in any of Claims 1--6 in which the fibre is positioned to be broken or deformed in response to the penetration of a wall.

9. Alarm equipment, to signal symptoms of intrusion into an area, including an optical fibre arranged to be broken or deformed in response to the penetration of a wall, whereby the transmissibility of light in the optical fibre is altered, and means to indicate an alteration in the transmission of light in the fibre.

10. Alarm equipment as claimed in Claim 9 comprising a source of light modulated in a recognizable pattern at one end of the optical fibre.

I 1. Alarm equipment including an optical fibre constructed and arranged substantially as herein specifically described with reference to figure 1 of the accompanying drawings.