Wired/Wireless Alarm Systems

Meindert Sprang wrote:

> Out of curiosity: what signal levels should a wireless alarm survive?

The short answer to this question is: whatever you claim in the product
documentation. The requirements on this are in the process of changing,
and the new requirements are (basically) to state the Tx power on
transmitters, and the minimum acceptable signal level on receivers.
Manufacturers put a _BIG_ derating factor into this for commercial
installs.

The UL tests are really complicated and can't be described in a
paragraph. They involve sweeping noise signals across wide ranges at a
"background noise" Tx power, the level of which is calculated with a
complicated method. (I am way oversimplifying this. I haven't actually
performed the test myself, though I've read it and discussed how to run
it on products for which I'm responsible).

It's nowhere near as simple as saying "xyz W CW (or 50% modulation or
whatever) Tx at abc range".

"larwe" <zwsdotcom@gmail.com> wrote in message
news:1143808660.768256.112160@z34g2000cwc.googlegroups.com...
>
> Meindert Sprang wrote:
>
> > Out of curiosity: what signal levels should a wireless alarm survive?
>
> The short answer to this question is: whatever you claim in the product
> documentation. The requirements on this are in the process of changing,
> and the new requirements are (basically) to state the Tx power on
> transmitters, and the minimum acceptable signal level on receivers.
> Manufacturers put a _BIG_ derating factor into this for commercial
> installs.

So no guarantee then.

> The UL tests are really complicated and can't be described in a
> paragraph. They involve sweeping noise signals across wide ranges at a
> "background noise" Tx power, the level of which is calculated with a
> complicated method. (I am way oversimplifying this. I haven't actually
> performed the test myself, though I've read it and discussed how to run
> it on products for which I'm responsible).
>
> It's nowhere near as simple as saying "xyz W CW (or 50% modulation or
> whatever) Tx at abc range".

Mmm.... unfortunately it is as simple as putting a big enough carrier on the
right spot to blank any receiver. That is just a basic fact. So I still
think that a wireless security system has no security at all.

Meindert

In article <122qc60knk57aff@corp.supernews.com>, Meindert Sprang
<ms@NOJUNKcustomORSPAMware.nl> writes
>"larwe" <zwsdotcom@gmail.com> wrote in message
>news:1143808660.768256.112160@z34g2000cwc.googlegroups.com...
>>
>> Meindert Sprang wrote:
>>
>> > Out of curiosity: what signal levels should a wireless alarm survive?
>>
>> The short answer to this question is: whatever you claim in the product
>> documentation. The requirements on this are in the process of changing,
>> and the new requirements are (basically) to state the Tx power on
>> transmitters, and the minimum acceptable signal level on receivers.
>> Manufacturers put a _BIG_ derating factor into this for commercial
>> installs.
>
>So no guarantee then.
>
>> The UL tests are really complicated and can't be described in a
>> paragraph. They involve sweeping noise signals across wide ranges at a
>> "background noise" Tx power, the level of which is calculated with a
>> complicated method. (I am way oversimplifying this. I haven't actually
>> performed the test myself, though I've read it and discussed how to run
>> it on products for which I'm responsible).
>>
>> It's nowhere near as simple as saying "xyz W CW (or 50% modulation or
>> whatever) Tx at abc range".
>
>Mmm.... unfortunately it is as simple as putting a big enough carrier on the
>right spot to blank any receiver. That is just a basic fact. So I still
>think that a wireless security system has no security at all.
>
>Meindert

All security is relative. You only need to have a defence that stronger
than the likely attacker. Wireless or wired is irrelevant of the local
thugs are going to ram raid with a truck. 

Most houses can use wireless because 99% of house breakers are not going
to be electronics/computing  geniuses. Those types are tucked up safe
and warm at home and causing mayhem in data centres from their bedrooms
by hacking with a PC.

 

-- 
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
\/\/\/\/\ Chris Hills  Staffs  England     /\/\/\/\/
/\/\/ chris@phaedsys.org      www.phaedsys.org \/\/\
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/

"Meindert Sprang"  Wrote:

> Mmm.... unfortunately it is as simple as putting a big enough carrier on 
> the
> right spot to blank any receiver. That is just a basic fact. So I still
> think that a wireless security system has no security at all.

I've heared this argument many times before on security newsgroups. There is 
never any argument that a wired system is more reliable than a wireless 
system.

I guess it comes down to practical experience. In my experience I've never 
known a real situation where someone is transmitting permanently 
on-frequency and destroying the alarm panels ability to receive signals. Yes 
it is a possibility, but probably quite rare.

When installing and testing an alarm panel an installer can easilly check 
for problems such as high background RF in fixed installations and make a 
decision to install wireless or wired based on a pre-installtion visit.

In the event of someone deliberately deciding to transmit high RF 
on-frequency with the intent the break into a premesis protected by 
wireless, then an armed alarm panel will detect jamming and go into a tamper 
alarm. The panel has done its job and signalled an alarm event. Just what 
you would want it to do.

What appears to be the bone of contention is that someone unwittingly 
transmitting on-frequency permanently will also cause the alarm panel to go 
into a tamper alarm condition. Yes, this could happen. In my experience (so 
far) I've never heared of a single verifyable occurrance.

Jim

Larwe Wrote:
> 
> Lets hope that James (original post) has an unencrypted panel. Or better 
> still, has decided that the time and effort involved is too great. I know I 
> wouldn't be able to find the spare time necessary to undertake such a task.

Larwe, all,

Thanks for the help.  We were attempting to adapt an existing OEM keypad 
for use with our system.  Based on this feedback, other research, and a 
slight expansion of the requirements, we're now designing our own keypad.

 From time to time you just have to invent the wheel whether you want to 
or not.