Polycom Phones on VG224 and post-call dialing

[john.heyer]

We're having an interesting problem with a VG224 that has several Polycom conferences phones attached on the FXS ports. The Polycom user reports being able to get a dialtone and connect OK, but if they try to enter digits after the call is established, nothing happends. Everything works fine when dialing from a Cisco IP phone. The VG224 is MGCP, and it uses a H.323 gateway to connect to the PSTN. Could this be an issue with DTMF relay configuration? I've been having trouble understanding exactly what DTMF relay does for me.

[Aaron Harrison]

Hi John

Basically when you dial a number from a phone, the gateway you are attached to will convert the tones generated from the handset into a number and will route the call based on this.

When a call comes into your H323 gateway (assuming it's ISDN) the numbers come in through the D-channel and the call is routed accordingly..

DTMF relay comes in after the call is set up between the two endpoints - if you dial a digit, this digit needs to be transported between the endpoints... This doesn't work particularly well when put through codecs designed for voice, so you need the local gateway to which the polycom is attached to convert the DTMF tones from the handset into signalling, and pass this to the H323 gateway where the opposite happens and the same tones are (hopefully) generated at that end...

When using CM, you would normally have dtmf-relay h245-alphanumeric configured on the dial-peer pointing to callmanager.

As the VG224 is an MGCP gateway I believe you'll need the command

mgcp dtmf-relay CODEC all mode out-of-band

Although in all honesty I've never used a VG224..

Regards

[john.heyer]

Seems that could be it, then. Here is the line:

mgcp dtmf-relay voip codec all mode nte-gw

I'll put this in the configuration on the VG224 and see if this helps.