Re: 45. Professionals always say that the latest wireless alarm system

["Roger" <rumble@xxxxxxxxxxxxxxxxx>]

> Can you specify what item of the EN50131 specify that it test:
> - transmitter voluntary generated interferences with
>  unreasonable signal strength ON the alarm frequency
Speak English. If you are asking how is it tested then that's a whole
document on its own. However I can tell you from experience that apart from
testing and generating a jamming signal throughtout the whole tested
spectrum as part of RFI immunity tests, the test houses ask you to provide
an identical product to that being tested BUT that the identical product is
set to permanent transmit mode. In this way the test house can be assurred
that the jamming signal is at exactly the same frequency. Of course, they
check it using a suitable spectrum analyser to make sure no-one is trying to
pull a fast one. The test checks that the detectors and receivers cannot
receive during the test. This is a simple thing to do. The test then records
how the equipment deals with the jamming and this is checked against the
grade that the equipment has been submitted for. Finally the jamming signal
is removed and the EUT is re-tested to ensure that operation resumes as
normal.

> and
> - not test the allowed internal generated signal levels produced
>   by other equipments who conform to the maximum authorized
>   stray signals?
Again, your question makes no sense to me. Your English is very bad here. I
think your trying to ask how is th eequipment tested to ensure that it
continues to perform correctly when other normal equipment is in the
immediate vicinity?. If that is your question then all you have to do is
read the standards. I guess from your questions that you don't have any
copies of the appropriate documents. It seems very strange to me that you
spout on about RFI and alarm equipment, yet you have no working knowledge of
how security products are tested and expected to perform in todays market
place. I believe I have given you the answer to this one before but just in
case you forgot again... 868Mhz has strict usage and band occupancy rules.
The rules specific to band occupancy states that the equipment must not use
more than 1percent of the band. This is tested at test houses very simply
and can be seen and measured on suitable equipment. If other equipment is
operating in the vicinity on the exact same frequency then this equipment
will also be subject to the same rules. All devices on the band use a method
whereby they 'listen' before they transmit. If other transmissions from
other equipment is detected then the equipment holds off and tries again 1%
of the band later. This allows a theoretial 100 pieces of equipment on the
same band in the same area transmitting at almost the same time. The methos
generally used also uses some of the 'hold-off' and retry methods used in
Ethernet which is often described as RF over a wire. We all know that
Ethernet is pretty reliable and so the same methods used in wireless work
quite nicely.

Paul, if you have any EN5031 or other standards questions I suggest you
purchase a copy of the relevant documents yourself. I could answer your
questions all day but I get the impression that no matter what I or anyone
else tells you, you will ignore it or ask som eother dumb question.

In fact why don't you go out and purchase a brand new state of the art
wireless system from a reputable manufacturer and see for yourself just how
good they are these days. If I was you I'd go for 868MHz and prefferably
2-way.  Then try to break it. You'll find jamming detection works a treat
and all of your misconceptions about wireless unfounded. Don't buy cheap
crap. You get what you pay for. You pay peanuts, you get peanuts.