ATA 190 with Modem line

[abecquet-LP]

Hi everyone,

We deployed on our company the ToIP system, we need keep some old analog phone, so we deployed some ATA 187 and 190. Our problem is the following:

• We have 2 analog lines behind 1 ATA 190, each line is connected to a modem, in order to send information to a gaz company.
• The modems send data with protocol G711, but they are unable to communicate with the supplier, and the supplier get busy line when he tries to communicate with these 2 modems.
• From CUCM, we tried to modify the settings on this ATA 190 box as follow, but without success:
• Modem line : ON
• • Fax mode to :  g711ulaw
  • Fax mode to :  g711alaw
  • 

So does the ATA 190 are compliant with modem using protocol G711?

[Dan Lukes · Accepted solution]

At the first, your question needs to be clarified. Modem is connected via analog line to ATA190. It doesn't use G.711 digital encoding to transmit their data. Based on their capabilities and configuration it use analog protocols - one of V.22,V.22bis,V.26bis,V.27ter,V.32,V.32bis,V.32terbo,V.34,V.90,V.92 (or some Bell variant).

It's not attempt to educate you for nothing, it's important for your issue.

Modems use initial handshake to select particular protocol according the protocols supported and line condition. Unfortunately, they may overestimate line quality. It's known issue on digital lines including VoIP. As a result, they are unable to communicate using selected protocol as the line quality is not good enough for it.

Solution is simple in most cases. Configure your modem not to use high speed protocols. Consider 9600bps and V.32 to be maximum. It's not necesarry to change configuration of modem on opposite side. As your modem will not announce high speed protocols in their capability list, the connection will be established with slow speed and should be more reliable regardless the other end settings.

The metering data are rather small, thus slow speed will not cause unacceptable increase of transmission time.

Note that you should turn "Echo cancellation" to off for modem communication.

[abecquet-LP]

Hi,

Thanks for your explaination, I will check it, and make some tests after our ToIP's supplier back in a week to test the cables between the modems and ATA 190.

I will be back to keep you inform.

[abecquet-LP]

Hi,

just for information, we had another ATA 190 with also same problem, in fact there was two problems :

1. An error in the cables connexions w<hen out telecom supplier manage the 2 new ATA boxes, which resolved one of the two suppliers connexions
2. And you explained a speed setting from the other supplier, as they could not change it, we succeed to connect them through 2 real analog lines we still have but unused

the problem has been resolved.