Re: 24. RF Interference detection, does it exists on Wireless Alarm System ?

[-pull@shoot]

On Mon, 30 May 2005 02:41:27 +0200, -pull@shoot wrote:

>
>Everybody knows that wireless alarm systems are unreliable during
>Radio Frequency Interference (RFI) because the transmission path of
>signals between sensors and wireless receiver is muzzled by an
>external transmitter causing RFI.
> Wireless is unreliable during RFI, and there are a tremendous number
>of sources who generate it, theyre number increases day by day..
>    YOU WILL NOT BE WARNED THAT YOUR WIRELESS SYSTEM is DEAD.
>
>Is RFI detected?
>Let's see what "so called" professionals say about the lack of the
>sensor data reception detection circuit.
>
>All wireless alarm systems have tamper and battery low detection.
> The presence of an extra bit(s) in the coded sensor transmitted
>signal stream allow the control panel to identify the occurrence of
>tamper or battery low.
> Some of the so called pro's attempt to convince you and say that this
>is also useable and effective for RFI detection..
> Everybody knows that no valid signal reaches the wireless receiver
>during RFI.. how can that work when transmitted signal and there
>detection just fail because RFI jeopardize the RF loop signal
>validity???
> Forget it, its sellers talk.
>
>In some new and recent systems each sensor transmit on a regular basis
>to the panel an "I'm here" signal. The panel takes note if all are
>received correctly within a certain timespan. Some systems have a
>signal strength indication to.
> This design feature is used to check validity of the sensor reception
>signal at installation.It allow to see if all sensors are located at a
>receiver signal reachable place.
>
>Note:
>      If this feature is always left ON, it detects continuously
>      sensor transmission failures and sensor position problems caused
>      after installation due to the displacement of conductive objects
>     (statues, car and other metal objects).
>       The displacements of a conductive object alter the RF signal
>      path by masking completely or partially (attenuation) the
>      transmitted signal to the receiver, the signal decoding of the
>      system fails.
>
>Most of the time the installers "disable and put OFF this feature"
>because it don't identify typically RFI from sensor "transmission
>path" failure, both occult signal reception validity.
> There is a way around the problem, metal object obstruction is
>usually for a rather relative long timespan before it is removed
>(statue, car), by tuning up the time delay the system can warn lack of
>sensor signal and +/- avoid false alarms.
> This works and is effective for long (hours) time delays before
>warning occur, unusable to detect intruder generated RFI.
>
>Until now, according to pro's, no interference warning has been
>received at central stations during 20+ years..
> Conclude yourself of the efficiency of that RFI detection...
>
>Why doesn't the most recent developed systems not detect typically
>interference situation?
> Because there are several interference sources, situations,
>impossible to identify them (see diversity of sources i described) and
>during that time, the wireless systems are muzzled, dead.
>
>
>Conclusion:
>Assume that there is some kind of detection that really works(?), it
>don't solve the muzzling and intruder "detection" during
>interferences.
> You think there are systems who detect RFI, well try it out with a
>RFI generating transmitter preferably in a crowded wireless users area
>at night and see how many nightmares it will cause, police adventures,
>and more..
> Good luck