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Wired/Wireless Alarm Systems

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".

Reply to
larwe
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So no guarantee then.

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

Reply to
Meindert Sprang

In article , Meindert Sprang writes

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.

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

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

Reply to
Jim

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.

Reply to
James Dabbs

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