Showing results for 
Search instead for 
Did you mean: 

Inbound Modem calls using a VG224

Level 1
Level 1

I have a customer site where we have a VG224 providing analogue ports for fax machines/franking machines and modems. All using G.711 passthrough direct to the PSTN gateway.

Fax machines work no problem. Franking machine works no problem. Outbound modem calls work better than expected. They actually connect at 52.0Kbs second.

However, one of the modems has to recieve calls from a central security function to access the cctv application that runs on a standard Dell PC running Windows XP. Outbound call from the PC to the internet works fine connects 52.0Kbs. When we attempt to dial into the PC the orginating modem states it doesn't get a carrier signal. The modem log on the receiving PC indicates that the call connects then drops within milliseconds stating no carrier.

I have been running various debugs on the VG224 which shows it connects but I cannot determine what is happening next. a debug voip hpi all appears to indicate that the VG224 is seeing CM tones and Modems tone but I cannot determine from where these tone are coming from.

Does the VG224 need some specific configuration when receiving modem calls as oppose to initiating them.

As always any advice greatly appreciated.

3 Replies 3

paolo bevilacqua
Hall of Fame
Hall of Fame

First you should check and specify if using modem pass-through, or relay.

I did state I am using G.711 passthrough in opening paragraph

Sorry for having missed that.

Unfortunately modem over VoIP is not guaranteed to work and that's the reason why modem relay was introduced.

Alternatively if possible, use an FXS card in the same router that has PRI.