[WXC/VFX] Modems and Vfx

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Phin

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#13890 3-Jun-2007 10:11

Has any body had any issues with standard modems (not dial up)and Vfx
I can't seem to connect to my alarm panel when ringing from my Vfx number. However when I call a dial up provider i get excellent connection speeds, 52K. The alarm panel uses an inbuilt modem. there is noting special about it. Also the fax works fine on the vfx line. I have connected to the alarm panel trough the normal phone line so the problem is specific to the Vfx line.
Any help appreciated
Thanks Nathen

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#73291 3-Jun-2007 10:26

Do you know what codec you are using at all?

Modems are something that in a nutshell aren't really designed to work over VoIP connections. It's true that over a perfect connection using ulaw or alaw they will work however using a compressed voice codec such as g729 will result in them failing to work. Many alarms only use a 1200bps modem so if you are using ulaw or alaw you should get it working OK - many also aren't a modem as such, they simply dial a preprogrammed number and send DTMF tones.

From rereading your post however I've just realised that you're probably referring to connecting to the alarm from a remote phone number to arm/disarm it. How is your alarm set up to answer incoming calls? Many require you to ring for x number of rings and they will then answer on the next call immediately. Also how old is the alarm and was it previously hooked into a jackpoint or hardwired? If it was jackpoint do you know if it was a 2 or 3 wire jackpoint?

grant_k

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#73292 3-Jun-2007 10:29

Hi Nathan,

Using analogue modems with VFX is a difficult area. Basically, they either work or they don't, there's not too much can be done to change anything in this regard, as VFX is primarily designed for Voice, with Fax support provided on some ATA devices.

I have tried 2 different modems on VFX as follows:

1) The modem in MySky works OK (I think it is an older type running at 28.8kbps or slower)
2) The 56kbps modem in my Laptop doesn't work, even after a lot of playing around with initialisation strings etc

I think you were quite lucky to get 52kbps using a dialup modem. I couldn't get that to work at all.

Regarding the modem in your security panel, the only thing you could check is to make sure that your ATA is actually using the G.711 codec when your security panel is communicating. You can check this via the ATA's status page, as you are probably aware. Because your fax is working, your ATA is obviously capable of using the G.711 codec. Just make sure that it is actually doing that while the security panel is communicating.

If the G.711 codec is not in use for whatever reason, Maverick may be able to help.

Failing that, you may need to look at an alternate way of connecting to your alarm panel such as via a cellphone link (using CSD), or upgrade the security panel to use an Ethernet connection instead of the analogue modem.

I hope that helps.

Cheers,
Grant.

Fraktul

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#73356 4-Jun-2007 00:42

Even with G.711 fax support does not work well as some faxes are pretty strict on the timings that will work with them reliably.

If T.38 is supported then you should use this for fax where at all able.

Phin

42 posts

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#73362 4-Jun-2007 08:37

From rereading your post however I've just realised that you're probably referring to connecting to the alarm from a remote phone number to arm/disarm it. How is your alarm set up to answer incoming calls? Many require you to ring for x number of rings and they will then answer on the next call immediately. Also how old is the alarm and was it previously hooked into a jackpoint or hardwired? If it was jackpoint do you know if it was a 2 or 3 wire jackpoint?

The alarm is less tyhan a year old and it uses a modem in it proper form. Ie negotiated then communicates with etc, not dial tones.
The alarm is connected to a standard tele line so the problem is not the alarm end because that works if you dial from a normal line. Also the alarm answers the call just the 2 modems don't successfully negotiate when I use the voip.

sbiddle

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#73367 4-Jun-2007 09:19

Phin: The alarm is less tyhan a year old and it uses a modem in it proper form. Ie negotiated then communicates with etc, not dial tones.
The alarm is connected to a standard tele line so the problem is not the alarm end because that works if you dial from a normal line. Also the alarm answers the call just the 2 modems don't successfully negotiate when I use the voip.

Unfortunately it's possibly one of those issues that you may not be able to solve unless you want to spend a lot of time trying various configurations.

Lots of alarm companies are moving towards cellular options these days since you can monitor the alarm in realtime however these are nowhere near as cost effective (around $400 for a basic unit) and also have ongoing costs associated with them.

Fraktul

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#73380 4-Jun-2007 13:19

You could try lowering your baud rate on the dialing modem via init strings, this may increase the chance of it working. The modems should attempt to try this themselves during handshake however it is possible this is not occurring correctly.

Phin

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#73433 5-Jun-2007 11:30

Grant17: Hi Nathan,

Using analogue modems with VFX is a difficult area. Basically, they either work or they don't, there's not too much can be done to change anything in this regard, as VFX is primarily designed for Voice, with Fax support provided on some ATA devices.

I have tried 2 different modems on VFX as follows:

1) The modem in MySky works OK (I think it is an older type running at 28.8kbps or slower)
2) The 56kbps modem in my Laptop doesn't work, even after a lot of playing around with initialisation strings etc

I think you were quite lucky to get 52kbps using a dialup modem. I couldn't get that to work at all.

Regarding the modem in your security panel, the only thing you could check is to make sure that your ATA is actually using the G.711 codec when your security panel is communicating. You can check this via the ATA's status page, as you are probably aware. Because your fax is working, your ATA is obviously capable of using the G.711 codec. Just make sure that it is actually doing that while the security panel is communicating.

If the G.711 codec is not in use for whatever reason, Maverick may be able to help.

Failing that, you may need to look at an alternate way of connecting to your alarm panel such as via a cellphone link (using CSD), or upgrade the security panel to use an Ethernet connection instead of the analogue modem.

I hope that helps.

Cheers,
Grant.

Tried 2 different modems both get 52 connection neither connect with alarm and Ata using G711u, Ethernet upgrade expensive, Hadn't thought of cellphone via ir port, though. might give it a try.

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Niel

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#73441 5-Jun-2007 13:12

How much is the upgrade to Ethernet monitoring?
Do you know of companies that offer Ethernet monitoring?
Do you want to monitor the alarm yourself, or get an alarm company to monitor it?

You can never have enough Volvos!

Niel

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#73442 5-Jun-2007 13:17

Something else you can try, connect an ADSL line filter between the modem and the VFX port. Maybe the digitally generated signal from the modem is such that the frequencies are too high for the VFX port to convert properly, or digital noise from the VFX port messes up the modem. The line filter will help to limit high frequencies in both directions.

You can never have enough Volvos!

Phin

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#73458 5-Jun-2007 15:20

Niel: Something else you can try, connect an ADSL line filter between the modem and the VFX port. Maybe the digitally generated signal from the modem is such that the frequencies are too high for the VFX port to convert properly, or digital noise from the VFX port messes up the modem. The line filter will help to limit high frequencies in both directions.

Ill try but I'm pretty sure the adsl filter stopped the alarm. This is because when the alarm was originally installed by the installer he managed to get it on the wrong side of the filter and couldn't connect to it. As for the price of the eathernt connection because the alarm is a professional alarm( i.e not a mitre 10 job or installed by your average electrician, had to be installed by a certified registed security personal) you are talking upper hundreds of dollars
Yes I do monitor the alarm. You talk to the alarm with a specific applacation and it looks like it just an't going to work,

richms

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#73508 5-Jun-2007 19:36

Can you do it thru a serial port and just put a lantronix type thing on your lan to get a direct IP connection to it over the internet?

Richard rich.ms

Fraktul

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#73518 5-Jun-2007 20:35

Niel: Something else you can try, connect an ADSL line filter between the modem and the VFX port. Maybe the digitally generated signal from the modem is such that the frequencies are too high for the VFX port to convert properly, or digital noise from the VFX port messes up the modem. The line filter will help to limit high frequencies in both directions.

Modems send and receive analog signals between themselves, not digital.

Niel

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#73534 5-Jun-2007 21:12

I am an electronic engineer, been designing electronics for 21 years. I am trying my best to put it in simple terms so most people would understand, while English is my second language. An analogue modem generates the analogue signal with a digital signal generator, it is digitally generated. Watch this space for an update...

You can never have enough Volvos!

Fraktul

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#73553 5-Jun-2007 23:42

All well and good my friend :)

But really, a lowpass filter is rather grasping at straws IMO if there is no noticable noise. He is the eletrical engineer though to feel free to ignore me ;)

Also if you have a spare filter lying round you have nothing to loose by trying this.

Cheers

Phin

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#73593 6-Jun-2007 10:47

The Adsl filter thing.
I also have lots of experience with electrical and electronics but I've been wrong to many time to say anything with certiaty any more, but here is my thoughts on the Adsl filter.
Adsl is relatively high frequency
modem/fax/voice is relatively low. Modem being modulated signal on low frequency the the human ear can hear.
Alds filter is low pass filter, stops high lets low, This is why you can still use fax,modem on a ptsn line with an adsl filter attached.
So why won't the security modem work behind a Adsl filter, NO IDEA but it didn't. All the installation information tells you to connect the alarm first in the line.
I'm not doubting anyone's information after all I came looking for help, But I think the problem lies in timing issues within the Voip protocol.
Another interesting fact I decovered is that the manfacture has stated that they have done extensive testing in the USA and their alarms are compatible with VOIP. The plot thickens.
Also I'v found some references on the net to a VOIP standard to ensure legacy compatibility with modems the standard is V.150.1 or mvoip.
I'm going to try the filter on the Voip line just out of interest though
Maybe Maveric can shed some light in the other standard.
regards

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