Reply by James Dabbs April 4, 20062006-04-04
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.
Reply by Jim March 31, 20062006-03-31
"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
Reply by Chris Hills March 31, 20062006-03-31
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 \/\/\ \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
Reply by Meindert Sprang March 31, 20062006-03-31
"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
Reply by larwe March 31, 20062006-03-31
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".
Reply by Meindert Sprang March 31, 20062006-03-31
"larwe" <zwsdotcom@gmail.com> wrote in message
news:1143801854.432295.246340@i39g2000cwa.googlegroups.com...
> > Paul Keinanen wrote: > > > My point is that the communication should not be easily jammable, e.g. > > use cables within the premises rather than radio technology. > > Are you familiar with the UL clash tests for wireless security and fire > safety appliances?
Out of curiosity: what signal levels should a wireless alarm survive? I'm asking because I find it very hard to believe that such a system, whatever sophisticated modulation methods they use, will keep working if someone transmits a 50W modulated carrier within a few tens of meters of that system. Meindert
Reply by larwe March 31, 20062006-03-31
Paul Keinanen wrote:

> My point is that the communication should not be easily jammable, e.g. > use cables within the premises rather than radio technology.
Are you familiar with the UL clash tests for wireless security and fire safety appliances? Wireless sensors are universally approved for use in, and sometimes the only practical choice for, both residential and commercial burglary and fire warning systems.
Reply by Paul Keinanen March 31, 20062006-03-31
On Thu, 30 Mar 2006 19:50:52 GMT, "Jim" <tech@picmodules.com> wrote:

> >"Paul Keinanen" Wrote: > >> And after a few weeks of such events without any other consequences, >> do you expect that anybody would pay attention to them ? >> > >Oh there are consequences!. For example (and depending on the installers >setup), the panel can be forced to not allow arm if certain faults exist. If >the user decides to ignore the persistant fault noise, ignore the fact that >the keypad is reporting a jamming fault, ignore the fact that the panel >cannot arm, then hey, that user has already made the decision that they >don't care if thet are burgled. At the end of the day the ownes is on the >user. The alarm panel has done its job of informing the user that a problem >has occurred and needs attention.
You just proved my point. The user will eventually disable the "false" alarms and easily also ignore real alarms, if the system generates a lot of spurious alarms due to bad design. IMHO, to be dependable, an alarm system must generate far less false alarms than real alarms.
>>Then one night during the blackout something else happens :-). >What, not a battery backed panel?. If theres a blackout then I guess the >inteference cause will now not be operating. Guess the battery backed panel >can now work even better. :-)
I was not referring to main failure. In radio communication "blackout" usually refers to complete loss of communication, often on a large number of frequencies. One the radio link is once again jammed, but the event is ignored as a nuisance, then it is time for the bad guy to act. My point is that the communication should not be easily jammable, e.g. use cables within the premises rather than radio technology. Paul
Reply by Jim March 30, 20062006-03-30
"Paul Keinanen" Wrote:

> And after a few weeks of such events without any other consequences, > do you expect that anybody would pay attention to them ? >
Oh there are consequences!. For example (and depending on the installers setup), the panel can be forced to not allow arm if certain faults exist. If the user decides to ignore the persistant fault noise, ignore the fact that the keypad is reporting a jamming fault, ignore the fact that the panel cannot arm, then hey, that user has already made the decision that they don't care if thet are burgled. At the end of the day the ownes is on the user. The alarm panel has done its job of informing the user that a problem has occurred and needs attention.
>Then one night during the blackout something else happens :-).
What, not a battery backed panel?. If theres a blackout then I guess the inteference cause will now not be operating. Guess the battery backed panel can now work even better. :-) Jim
Reply by larwe March 29, 20062006-03-29
Paul Keinanen wrote:

> If the system works on any license free band, such as the ISM bands > with other industrial and medical radiators (e.g. 2.45 GHz), it would
Empirically I can tell you: millions of installed systems -> no appreciable problems.