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Posted by Roger on May 30, 2005, 8:46 am
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Do you have a life or are you a resident in some kind of white jacket
institution ?.
>
> 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
>
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