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VoIP and Home Security Systems Don't Get Along
coondoggie writes "Here is a story about consumer VoIP services that can cause your home security alarm system to malfunction or not work at all. There have been problems with customer phone systems in Canada who were using Primus but Vonage customers in the U.S have complained too. A number of sites have popped up offering suggestions to help deal with the problem."
Here is a story about consumer VoIP services that can cause your home security alarm system to malfunction or not work at all.
This would present quite a difficulty, if say, your home security system was ED-209.
Wizard Needs Food, Badly
I don't mean to be mean, but home broadband connections and VoIP services do not meet the same standards of reliability and uptime that your landline is generally required to meet.
Whether it is 911 service or your home's alarm system, do you want to trust your home broadband connection for emergencies?
If you''ve got VOIP, you've got an IP network.
Get an alarm system that uses your IP network rather than legacy POTS network.
Depend for emergency communication on a shared bandwidth communications link whose functioning depends on utility power availability coupled with some ISP's service plan, and maybe when the bad guys break in you won't get the call? Huh? You think? Or, to put it another way, there's no guarantee that The Phone Company's own landline will work perfectly either, but if I had to bet my home on it, I'd go with TPC over VoIP. In fact, personally, I've stuck with TPC landline because of E911, because my landline has always worked during NYC blackouts even when my cellular phone didn't, and because I have yet to see a VoIP service provider that would guarantee that if some guy in Afghanistan (or Milwaukee, for that matter) somehow manages to clone my SIP identity and proceeds to make N-billion dollars (well, amounts are relative to my savings account balance) worth of international phone calls, that they won't hold my feet to the fire if I refuse to pay the bill. But of course, you may see things differently.
It smells because there are easy solutions to the problems. First of all, you can supply backup power to your ATA and not have to worry.
Secondly you should wire your setup as RJ31X so the alarm system can cut in and take control.
Thirdly - you can set your bandwidth so that fax and modem signals will work. Better yet, how come no alarm company has an IP based monitoring setup? Be pretty simple to do with VPN's, etc.
Finally the E-911 issue was resolved a long time ago. I have full E-911 service through Vonage.
All this leads me to believe that ILEC's are behind these stories. They're losing business left and right to less expensive VoIP carriers. And Verizon for one is in a particularly bad spot, their little fiber build out isn't generating the returns they expected.
To a single number. And hope that your security system HAS a local call-in number (it should anyway). The neat thing is, old fashioned phone lines are self powered and always work; you can get a dialtone that will only work with 911, 0, and a designated number for as little as $12/month in some cities. You can get 911 and 0 for free in most phone companies in the nation, this is called "basic dialtone service".
SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
Is anyone (here) surprised by this? It seems painfully obvious to me, that most such services obviously wouldn't work. That this guy wasn't notified BY THE SECURITY SERVICE that his alarm system wasn't functioning for over a year, speaks volumes about how useless that service really is.
It's only too easy to cut a POTS line, or tie it up by dialing-in to it, which is exactly what any competent burglar will do... Maybe with a (pre-paid?) cell-based service, your alarm will have a fighting chance, but not a lot even then.
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
works great, doesn't require any phone line, and has gone down in price recently.
POTS lines are no longer needed.
What are the Arabian stallions in your bedroom really for?
http://michaelsmith.id.au
Most houses have access to the POTS from the outside. It is just as easy for the "bad guy" to snip the POTS line as it is for them to shut off the power. Given that batteries on alarm systems are well known, it seems more likely that the "bad guy" would go the route of snipping phone lines over cutting power. Of course if the alarm is set to call over VOIP, or even as a TCP/IP, the "bad guy" would have to worry about cutting the phone line, the cable line, AND knocking the satellite dish out of alignment.
Caveat: some of their links were broken the last time I checked. Makes you wonder.
Obligatory disclaimer: I've just hit their website looking for a similar solution; not a customer (yet).
DT
Is this thing on? Hello?
According to the Allied Fire & Security firm firm
I ALWAYS want my firms to be firm.
--
"Outlook not so good." That magic 8-ball knows everything! I'll ask about Exchange Server next.
Used to work at an ISP that did VoIP (wirelessly in fact). If you could tweak the baud rate on your security system and drop it down to say 1200bps, it would typically work. It was still fairly hit and miss though. Add to that that many customers had no clue how to do this and alarm companies didn't care enough to try and help them.
Modem-type communications expect timing to be near exact (something the PSTN can guarantee) and just don't work well with the random delays (caused by 'net conditions, jitter buffering, etc) that are inherent with VoIP. T38 helps with faxing, but any sort of modem connection is going to cause problems.
We made sure our customers knew that burglar alarms were _not_ something we supported over VoIP. In fact it's a downright silly idea tying your home protection in with your Internet connection in most cases anyways. You can often get a phone line specifically for burglar alarms for less than you'd pay for a line used for talking on as well, so this is typically what we'd advise customers to do.
There is a lot of signal degradation converting from analog to digital, lossy compression of the digital signal, and converting it back to analog. Not to mention the analog to digital conversion has to happen twice (once over the VoIP carrier, and again when it's received).
It's not just that.
POTS signals are generally converted to digital samples at the first switching center they hit (or at curbside equipment along the way), switched as a digital signal, and converted to analog again similarly near the far end. To avoid clicks and pops (and persistent phase jumps) the sampling rates at the D->A and A->D conversion must match - exactly. The phone companies use very accurate clocks, synchronized across their whole network, to make this happen.
The phone companies originally used digital just to pack multiple phone calls for a hop from one analog switching center to another - and D->A->switch->A->D converted at each switch - with synchronization only needed between the ends of the hop. This saved a lot on cabling and gave better signal than analog transport, but not as good as digital from one "last mile" to the other. Then they added digital switching to eliminate the degradation of the multiple A/D conversions and simplify the switch - and spent a decade or more getting clocking synchronized across the whole network to eliminate the resulting glitches. Even today, in the being-retired POTS network, "timing is a third of the problem".
(These days the clocks are synchronized even between carriers by essentially all of them getting their master clocking from the atomic clocks of the GPS system. Before that they used things like LORAN D - a pre-satellite clocking-based radio navigation system for ships - or generated them in their own committee of atomic clocks and distributed the clocking along with the signals using the carriers of the SONET optical fibers or the T1 and E1 carriers of copper and microwave days, and these methods are still used to synchronize boxes that aren't in installations big enough to rate their own satellite-derived clock.)
The signal is encoded as a "DS0" stream of 8,000 8-bit samples per second, in one of two closely related floating-point-like coding schemes ("A-law" or "u-law" where "u" is "mu"), depending on whether you're using European or American-style standards.
So the signal is only capable of carrying 64,000 bits per second. (In fact the LSB may be "stolen" every few samples for ringing, off-hook, and dialing information, so only 56,000 bps are reliable - and it's actually a bit lower since some code sequences are forbidden by a regulation.)
Modern modems are designed around this and try to use as much as possible of these bits for data. In typical ISP-type modem banks the ISP end is connected to the phone company by a digital link and can directly control the bits, without incuring an A->D penalty, so the downlink can approach 56k, with the modem figuring out the actual sampling boundaries as part of the decoding. The uplink (or both sides in communication between two modems on analog POTS lines) comes pretty close to it - though it has to sacrifice some bandwidth to use a coding scheme that can survive clocking-rate errors between the modem's transmitter and the digitizer.
Of course if your VoIP link uses compression to carry your signal in less than 64k bps of payload, you're totally hosed. (And many of them do. For starters, if you're working over a dialup line you don't HAVE 64k bps to use.) Your modem assumes it's working over the POTS network and tries to use the bandwidth. And its signal gets totally hashed by the compression.
But even if you have the bandwidth (or the modem figures out that it's got a "noisy link" and down-speeds), you're still hosed. Because the clocking used for VoIP A->D and D->A steps is just not stable enough for the modem to take advantage of the bandwidth in the digital link.
One of the big pieces of persistent fallout from the war between
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Vonage works just fine with my alarm system. The only thing I had to do to make it work was have the alarm technician set the system to dial *99 first in order to put the vonage ATA into "fax mode". This is supposedly needed to make vonage lines work with TIVO also.
Obviously the author of the article (and the submitter) didn't do their homework.
A great place to start looking for how to make your alarm work with Vonage can be found here
And as for the people posting that using VOIP for an alarm is foolish because all a thief would have to do is cut the power: A thief is more likely to cut the phone line going from the PSTN to your house than he is the power. He isn't going to think, "Hmm, this person might have VOIP. I'd better cut the power, the cable, and the phone line outside the house just in case".
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I too measure the effectivity of my home security system by the pound, the quantity of teeth it has, and how much poop it leaves in the back yard. Most people out there will not mess with a dog, much less two or three, and they don't need electricity or a phone line to be fully functional. POTS, VOIP, or whatever. Of course the Brink's home security system won't dump the trash, pee next to the door, and eat one of your shoes if you come home late from work.
...<snip>...Clocking is part of it, A/D and D/A another, but the compression algorithms used by the VoIP device itself are generally the main culprit of modem device failure. They are designed specifically to carry voice (hence the big V in VoIP), same as telephones and the POTS network were originally designed for, not modem tones. After all, why would someone want to send data via analog methods when a digital one is available, right? Oh yeh, faxes/creditcard machines/atms/alarms/firepanels/etc. There are solutions available. Unfortunately for the home consumer level products these probably are either not built into their systems, or they lack the ability to enable or configure them to mesh with the other end of the VoIP tunnel. On the higher end equipment, such as Cisco IAD style VoIP devices (routers with FXS cards basically), settings on the FXS ports can be tweaked to amplify the modem signal (boosting the gain and adding a DC offset voltage), altering filters and setting up special pass-throughs (fax T38 relay/mgcp modem passthrough), and special compression algorigthms can be applied to lines designated to be modem-type devices. Once this is done, however, that is all that line will be able to do, as voice itself is now not the intended data and is filtered out as a side-affect. The other end of the VoIP net, where/if it goes out to the POTS network (trunking gateways) must also understand these features so they can take the digitally packetized modem packets and re-assemble them correctly into a decent modem type noise for the POTs lines. For buisness grade, where the network is setup specifically for VoIP traffic, this type of traffic is expected, it is still sometimes difficult to get it working with 100% of the devices out there, and most modem devices will still only operate at a max around 33.6k. If you are using skyp/vonage/other consumer bring-your-own connection, good luck with that.
Tm
disclaimer: no, I dont work for Cisco, however I do work for a business-class VoIP provider that uses cisco equipment for its structured network, setup and QOS'd specifically for this type of stuff, including the end loop circuits (T1) and devices (IADs) at our customers' sites.
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