[WXC/VFX] VFX with ADT alarm panel (Paradox)

Forums › One New Zealand (including Vodafone, WxC, Farmside) › [WXC/VFX] VFX with ADT alarm panel (Paradox)

jpollock

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#16817 29-Oct-2007 15:10

O.k. it's time to get this sucker working. I've played around with it for about 6+ months now, and my wife is starting to get peeved.

What I have:

1) A copy of the alarm protocol spec (DCS ContactID)
2) A very keen alarm vendor (Paradox)
3) An extremely motivated tester/onsite engineer (me!)

What I have seen so far:

I have a snoop trace from my gateway. I see the correct digits going out, but it seems that the device might be missing the kiss-off that should be coming back. The kiss-off isn't a DTMF digit (but is a 2400hz signal), so that is probably understandable.

To try to fix it, I would like to start changing some settings on the connection. I would like to change:

1) change the codec to G.711 (a-law?)
2) change the DTMF handling to INBAND.
3) a technical contact inside WorldxChange

I'm hoping that the problem is in those settings. The standard has some pretty strict timings on DTMF digits, so detecting/converting them might be causing the problem, or it might be a mishandling of the kiss-off from the monitoring service.

Is it possible to change the codec/dtmf settings for specific DNs? I'm sure you guys don't want G.711 through your entire network just to solve my problem!

I'm getting a lot of flack because the alarm is beeping at 2AM to let us know that it can't reach the monitoring service, so any help you could offer would be appreciated!

Thanks

Jason

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joshp

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#92926 29-Oct-2007 15:59

Hi Jason,

In regards to the codec change, please PM me your VFX number and I will change it for you.. DTMF will require a few changes here on our end but please be aware that this is a change globally as well as the codec for that matter.. so all calls will have inband DTMF and use G711 as your preferred codec..

Thanks Jason..

Josh

http://wxc.co.nz

maverick

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#93318 1-Nov-2007 17:44

We are actaully looking to do some work with Alarms so this is quite timely , have a couple of ideas for this my self, can your alarm panel dial * Codes and insert a pause do you know ?, I will touch base with Josh to see what he has done with you but will probably talk to you about this myself

Yes I am a employee of WxC (My Profile) ... but I do have my own opinions as well

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jpollock

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#93413 2-Nov-2007 10:29

Testing update: G711 u-law - no joy. We might have more luck with a-law.

Maverick: Welcome back! From looking through the user guide (when the installer tried to solve it), there isn't any way to insert pauses, and the standard specifies those timings anyways, so the monitoring service is likely to reject them. There are other alarm boards that might work better, but a protocol change probably means switching monitoring services too.

Does anyone know of an analysis tool that will take a snoop trace and show me the frequencies in the RTP packets? I want to see if the kiss-off coming back is according to spec or not.

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maverick

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#93417 2-Nov-2007 10:43

Made one change on this , if you restart you box and give it a couple of minutes then try again.

Yes I am a employee of WxC (My Profile) ... but I do have my own opinions as well

https://www.facebook.com/wxccommunications

sbiddle

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#93418 2-Nov-2007 10:50

jpollock: Testing update: G711 u-law - no joy. We might have more luck with a-law.

Maverick: Welcome back! From looking through the user guide (when the installer tried to solve it), there isn't any way to insert pauses, and the standard specifies those timings anyways, so the monitoring service is likely to reject them. There are other alarm boards that might work better, but a protocol change probably means switching monitoring services too.

Does anyone know of an analysis tool that will take a snoop trace and show me the frequencies in the RTP packets? I want to see if the kiss-off coming back is according to spec or not.

You could try running Wireshark/Etherreal and recording the RTP audio to a wav file. You could then analyse the audio file to see what's happening.

jpollock

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#93419 2-Nov-2007 10:54

Sorry guys, I'm not at home, the test cycle is going to be overnight on this stuff. :)

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maverick

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#93421 2-Nov-2007 11:04

no problems, Just had a listen to your call to the alarm company, DTMF like tones are actaully heard it ries 3 times by the looks of it, would be interested in seeing the spec from them as well, alarms are going to be tricky as some use modems / tones, some DTMF etc but we will take a look, do they have a contact in Auckland ?

Yes I am a employee of WxC (My Profile) ... but I do have my own opinions as well

https://www.facebook.com/wxccommunications

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jpollock

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#93422 2-Nov-2007 11:05

sbiddle:
You could try running Wireshark/Etherreal and recording the RTP audio to a wav file. You could then analyse the audio file to see what's happening.

I couldn't figure that out immediately, so I figured I would ask (I did ask Google first though!), any ideas how to do this without clicking each packet and dumping the payload?

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joshp

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#93424 2-Nov-2007 11:10

in the new versions of wireshark you should be able select statistics and then rtp.. you can also select voip calls which will break down the call into ladder maps.. much easier to read signalling.. it will give you codecs etc.. be aware that wireshark does not support g729 streams as that is a proprietary codec :)

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jpollock

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#93435 2-Nov-2007 11:36

maverick: no problems, Just had a listen to your call to the alarm company, DTMF like tones are actaully heard it ries 3 times by the looks of it, would be interested in seeing the spec from them as well, alarms are going to be tricky as some use modems / tones, some DTMF etc but we will take a look, do they have a contact in Auckland ?

The standard is ContactID, there is a copy in the google cache from a Russian web site. You can also buy it really cheap from (I believe) ANSI, cheaper than from the alarm standards group themselves.

http://72.14.253.104/search?q=cache:GS-380EI2j8J:www.smartelectron.ru/files/DC-05_Contact_ID.pdf+contact.id+alarm+protocol&hl=en&ct=clnk&cd=2

I'm using ADT, according to Paradox, they don't want to change their monitoring equipment, since that will involve buying new stuff.

I'll PM you the email details for my contact at Paradox (my alarm manufacturer).

From what I understand, ADT only uses Contact ID.

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Niel

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#93604 3-Nov-2007 16:02

Don't know if you are one of the persons I've told about this: We got an AC Neilson HomeScan scanner where you scan your shopping and once a week the unit dials an 0800 number via a 33k modem. My wife ordered it without my knowledge, but I can gladly report that she is now sending it back because it is a lot of work for little reward.

The following is long and detailed, to cover a wider audience. It is actually very simple and worked for me.

Anyway, it simply would not work on VFX. Being an electronic engineer, my thoughts were that it is probably because of image frequencies generated due to the digital sampeling by the VFX box (not a fault, simply an artifact of digitizing). The problem gets worse if there are high frequencies close to the sample rate, that is why CD players use oversampeling so artifacts are at higher frequencies and easier to filter out. Modems are not designed with this in mind, in fact often filters are left out of modems (cheaper) and uses the limited bandwidth phone line as a low pass filter.

The signal generated by the modem is digital with sharp edges. The faster the rise time, the more high frequency components there are to make up the signal and the more artifacts appear of you digitize the sifnal without running it through a low pass filter.

Combine the concepts of the previous 2 paragraphs, and you will see that cheap modems designed for analogue phone lines does not work as well on VFX as you would hope. To get back to my problem, I've decided to add a low pass filter between the HomeScan modem and the VFX box to try and reduce the high frequency components which in turn should reduce the digital artifacts. Being an engineer, I've looked for things I could try in the middle of the night when all the shops were closed (actually I was too lazy to go to the shops, get components and build a circuit). So I used a normal ADSL line filter. All it is, is 3 connectors of which 2 are paralleled and the third has a low pass filter to remove ADSL signals from the analogue phone port. So if you consider the 3 connectors to be called "line", "modem" and "phone" then the line and modem connectors are parallelled and there is a low pass filter between those two and the phone connector. So if you plug your alarm dialler into the phone connector, and then plug an RJ11 cable between your VFX box and the modem connector, then you have a low pass filter between your alarm dialler and your VFX box. This completely solved the problem I had getting HomeScan to work over VFX, running all the standard VFX settings. This should work for you as well, because your alarm panel use simple DTMF signalling and receives a single frequency acknowledge signal. Just make sure that one of the connectors you use is the "phone" connector which is the only one going through the filter.

Something else that might be a problem is that I've found with my VFX when I call someone the first 2 or 2 rings sound distorted (broken up) and is probably while the connection is sorting out the timings or something. Your alarm panel expects a handshake signal between 0.5s and 2s after the call is answered (0.5s new systems, 2s old slow systems, as per the link you provided). If the alarm company system answers immediately, then the handshake signal could fall within that short period when VFX is still unstable and breaking up.

Hope this works for you.

You can never have enough Volvos!

jpollock

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#97135 27-Nov-2007 13:31

Sorry I went AWOL, it got crazy here.

Listening to the call as dumped by wireshark, the inband DTMF sounds dodgy (all crackly), and I'm not getting the kiss-off signal that I was getting before. Can we please try G711 alaw with the DTMF decoder turned back on? The bad DTMF could just be my playback software though. Maverick, you said you listened to one of the calls, how did it sound to you?

I'll see about putting them up publicly.

Neil - Thanks for that info, I've already tried the ADSL line filter, and it doesn't appear to have had any effect. My problem started out sounding like the alarm couldn't understand the kiss-off, but now we've gone on to having the monitoring service not providing it. :) Progress, just in the wrong direction!

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Fraktul

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#97151 27-Nov-2007 15:24

joshp: in the new versions of wireshark you should be able select statistics and then rtp.. you can also select voip calls which will break down the call into ladder maps.. much easier to read signalling.. it will give you codecs etc.. be aware that wireshark does not support g729 streams as that is a proprietary codec :)

I beleive its only g.729a/b which are proprietary, g.729e is non proprietary afaik.

DribblingBadger

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#97335 28-Nov-2007 12:54

Hi Jason,

you are honoured with my first post.

it seems that you are half way there by using wireshark to decode the G711 RTP stream. Once you have that playing in windows you can use a trial version of direct recorder to capture the DTMF playing within Wireshark to a .wav file (http://mp3-recorder.533soft-com.qarchive.org/_download2.html for the software.)

Now you can decode the DTMF within the .wav file using software from PAS found at http://www.pas-products.com/bin/PASLE32Demo.exe

alternatively you could use a hardware DTMF decoder such as a ZIAD as a tap across the analogue pairs.

good luck

DB

jpollock

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#97358 28-Nov-2007 15:50

Thanks for the extra info guys, I'll have a look at those tools and see if they sound cleaner than my linux playback.

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