GB2247553A - "Satellite receiver theft alarm systems" - Google Patents

Abstract

The alarm system has a sensor 9 mounted on the dish 1 or its support to signal mechanical disturbances. This can activate a local alarm (16, Fig 3, not shown) and/or its output may be transmitted through the main aerial 6 or a separate line (11, Fig 2, not shown) to activate a remote alarm (24, Fig 4, not shown). The system also has a detector 10 to respond to electrical changes in the aerial beyond normal satellite signals, which will activate an alarm (24) if that aerial is cut or disconnected. <IMAGE>

Description

"ImProvements relations to Security Systems" This invention relates to security systems and is concerned with the protection of satellite aerials for domestic use.

The introduction of domestic satellite aerials, which are located outside buildings and include high value electronics, has created a new form of theft, that of removing the expensive head amplifier alone, or both the amplifier and the dish aerial. The most common method of removing the equipment is to cut or disconnect the cable between the head amplifier and to release the bracket supporting the amplifier from the aerial itself. Since the devices are conspicuous and usually lie outside conventional burglar alarm systems, they are attractive to the specialist thief. The object of this invention is to provide protection to the equipment and to deter its unlawful removal.

According to the present invention, there is provided an alarm system for a satellite signal receiver, the system including a sensor mountable on the receiver and adapted for signalling mechanical disturbance, and a detector adapted and arranged to signal electrical interference with a transmission line from the receiver.

The inevitable result of removing the head amplifier or the dish or both is some mechanical movement which, if detected, can be used to generate an alarm. This may be on the receiver, in which case the thief will be warned as well, or it may be at a remote location, within the building for example, so that the thief will not be aware that he is liable to detection. Both forms of alarm may be used. Where there is a remote one, the signal may be transmitted via a dedicated line or as a radio signal, but preferably the co-axial signal cable that already exists will be used.

The sensor will need energising, and preferably it will incorporate its own rechargeable battery. Again, this can be connected to a charging source such as the mains through its own dedicated line, but preferably use will be made of the head amplifier power supply. A further, less preferred method is to charge by radio transmission.

Where there is a physical link between the receiver and an alarm to transmit the warning signal, severance of the main signal cable, and any separate line if that exists, will effectively neutralise the sensor that responds to mechanical disturbances. Hence the need for the detector responsive to electrical interference.

This preferably comprises a device connectable in the aerial link between the head amplifier of the receiver and the decoder or the television set, sensitive to the condition of the aerial circuit, and adapted to generate an alarm if that condition is outside pre-determined bounds or lacks a pre-determined stability.

The decoder referred to above is a unit necessary to process the satellite signals before onward transmission to the television set. While it is often separate at present, it can be expected to be incorporated in television sets increasingly in future.

The detector will preferably be installed inside the building where it will not be obvious to the thief. It is envisaged that, in due course, it may be incorporated in the decoder or in the television receiver itself.

The detector can operate on the principle that if the head amplifier is removed or the co-axial cable is cut, the resistance of the cable will alter very materially. It may go above one threshold or below another. This can be detected, and used to signal an alarm. Also, it can incorporate means for monitoring the aerial cable for a signal from the movement sensor on the dish bracket and for triggering an alarm when there is mechanical abuse.

The detector will also require energisation and again it will be preferred to provide this by a battery, rechargeable from the head amplifier power supply. Also, the actual alarm can be local and/or remote.

For a better understanding of the invention, some embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows the general arrangement of a satellite aerial and its associated T.V. receiver, Figure 2 is a detail showing a modification of the aerial assembly, Figure 3 is a block circuit diagram of a sensor for the aerial assembly, and Figure 4 is a block circuit diagram of a detector unit.

In Figure 1, a satellite dish aerial 1 is mounted externally of a wall 2. A head amplifier 3 is carried at the focal point by a bracket 4. The received signal is picked up by this and fed by a co-axial cable 6 through the wall 2 to a decoder 7, and hence to a T.V. receiver 8. The units 7 and 8 may be combined.

To protect this system a sensor 9 is mounted on the bracket 4, and is adapted to respond to mechanical disturbances. It is shown in more detail in Figure 3. In addition, a detector unit 10 is provided inside the wall 2 to monitor the signals fed through the cable 6. This is shown in more detail in Figure 4.

The head amplifier requires a power supply, and this is generally channelled through the co-axial cable 6.

Conveniently both units 9 and 10 are also energised from the same source. Also, any response from the sensor 9 can be fed directly down the co-axial cable 6, and this is the preferred arrangement as shown in Figure 1. However, it would be possible to have this separate and to have a dedicated connection 11 as shown in Figure 2.

Referring to Figure 3, the sensor 9 is coupled to the cable 6 through a low loss interface 12, and it incorporates both a vibration detector 13 and an antitamper microswitch 14 which closes should anyone attempt to interfere with the sensor, irrespective of vibration. Both these can energise an alarm circuit 15 which can set off a local alarm 16 and/or which can feed an alarm signal via the interface 12 to the cable 6. The sensor 9 incorporates a rechargeable battery 17 with a power unit 18 to trickle charge that battery when the system is switched on and to provide a regulated voltage to the other components either from the main power supply or from the battery when the system is switched off.

Referring to Figure 4, the detector unit 10 is also connected to the cable 6 through a low loss interface 19. It has two detectors 20 and 21, one of which will respond to a high impedance above a pre-determined threshold in the cable 6 and the other to a low impedance in that cable, below another threshold.

A sensor interface 22 is adapted to pick up signals from the sensor 9, as when the dish 1 is mechanically disturbed. All these components 20, 21 22 can operate an alarm circuit 23 which can set off a local alarm 24 or close a switch 25 to operate a remote alarm. The unit lo is energised by a rechargeable battery 26 with a power unit 27 similar to the unit 18.

Claims (9)

1. An alarm system for a satellite signal receiver, the system including a sensor mountable on the receiver and adapted for signalling mechanical disturbances, and a detector adapted and arranged to signal electrical interference with a transmission line from the receiver.

2. A device as claimed in Claim 1, wherein the sensor is adapted to operate an audible alarm.

3. A device is claimed in Claim 2, wherein the audible alarm is mountable in conjunction with the receiver.

4. A device as claimed in Claim 1, 2 or 3, wherein the sensor is adapted to operate an alarm at a remote location.

5. A device as claimed in Claim 4, wherein the communication between the sensor and the alarm is via the main signal cable of the receiver.

6. A device as claimed in any preceding Claim, wherein the power source for the sensor is a rechargeable battery, the charge current for which is provided through the head amplifier power supply.

7. An alarm device as claimed in any preceding Claim, wherein the detector is connectable in the aerial link between the head amplifier of the aerial and a decoder on or for a television set, is sensitive to the condition of the aerial circuit, and is adapted to generate an alarm if that condition is outside pre-determined bounds or lacks a pre-determined stability.

8. A device as claimed in claim 7 as appendant to Claim 4, wherein the detector is adapted to decode any signals from the sensor and to trigger the alarm if they indicate mechanical disturbances.

9. As alarm system for a satellite signal receiver substantially as hereinbefore described with reference to the accompanying drawings.