jak@mtgzz.UUCP (j.a.kushner) (01/22/86)
This is being posted for a friend who would like to have a home security
system installed in their house.
They have looked at INFRA-RED, and HARD-WIRED types and wondered if there
was a difference between them in terms of effectiveness and installation
(aside from the fact that the wires can be seen with the HARD-WIRED systems)
Any information would be appreciated.
Please respond by e-mail:
{...ihnp4!}mtgzz!jak
Thanks in advance,
Jeffstratton@brl-smoke.UUCP (02/06/86)
> This is being posted for a friend who would like to have a home security > system installed in their house. > They have looked at INFRA-RED, and HARD-WIRED types and wondered if there > was a difference between them in terms of effectiveness and installation > (aside from the fact that the wires can be seen with the HARD-WIRED systems) > > {...ihnp4!}mtgzz!jak > > Thanks in advance, > Jeff I have installed a number of residential security systems, know the state of the art in intruder detection, and feel that I could help clarify this somewhat apples-and-oranges question. As posed, the question seems to confuse intruder detection with the manner in which sensors are connected to the central control instrument. One can detect the presence of an intruder either at the perimeter of the protected area, or inside the protected area. Residential perimeter protection is commonly provided by switches on doors and windows that sense when the door or window is opened, or the glass in a window is broken. These switches and glass-break sensors are usually hard-wired into the home's central control box, although sometimes where it is impractical to run wires, a small radio transmitter is located at the door or window, and the receiver is installed near the central control box. A number of different motion-sensing technologies are being exploited to sense an intruder's presence in, and movement through a protected area: microwave, ultrasonic, and most-recently, passive infra-red. As the question posed seemed to indicate that IR sensing was one of the two choices to be compared, I'll address that mode. Passive IR sensors monitor the background temperature of the protected space. The temperature is sensed in multiple "mini-zones." As the temperature of the protected space changes during the day (or night), the same rise or fall of temperature is seen by the sensor in each of its "mini-zones" and the sensor takes this as a normal condition. Should an intruder enter the protected space, the temperature seen by the sensor in each mini-zone will increase relative to the others as the intruder moves about. The sensor takes this as abnormal, and an "alarm condition" results. This alarm signal is sent to the central control box either over wires (hard-wired), or as in the case of perimeter switches, a radio link could be used. There are on the market devices that use IR to communicate between a hand-held transmitter and a "slave" device, such as some tv remote controls, and even a bathroom scale where the weight indication is sent from the scale base to a wall-mounted display using IR instead of wires. IR is not, to my knowledge yet used in security systems to transmit a signal from sensors to the central control box. This still must be done by hard-wire or rf transmission. Hope this helped. **Please send responses, queries to brandal@apg-1.arpa.** Brad Randall <brandal@apg-1.arpa> A guest on this account.