Showing results for 
Search instead for 
Did you mean: 

Polycom RMX Gateway ISDN to Cisco MCU DTMF Problem

Level 1
Level 1

Hi All,

I currently have a Polycom RMX1500 on the latest software 7.8.1 in my VC environment. I also have a few Polycom HDX and VSX with ISDN installed.

We are currently moving all our units to IP only and they can utilise the RMX Gateway to break out on ISDN. This works fine when dialing straight to a VC Unit.

However, Once I try to dial into a Codian or Cisco MCU, I am not able to send through DTMF to the meeting room.

I have tried this to multiple Cisco and Codian MCU with the same problem.

When I dial the Codian MCU from a HDX or VSX ISDN then I am able to send through DTMF, but not through the RMX Gateway.

Can anyone assist in getting my DTMF to work please to a Codian/Cisco MCU please.


1 Reply 1

Level 4
Level 4

Please try switching off the advertise out of band DTMF option in Settings > Conference.

See description below

Advertise out of band DTMF

If this option is checked, the MCU advertises the ability to receive out of band DTMF.

If this option is checked, endpoints are allowed to send out of band DTMF. If this option is unselected, the MCU will not advertise the ability to accept out of band DTMF and endpoints will instead be forced to use in band DTMF.

Prior to release 4.1, the MCU always advertised  to endpoints the ability to receive out of band DTMF tones. Now you can disable this functionality if required. If you unselect this option, endpoints are forced to send DTMF in band (in the audio channel). This means that the MCU  can pass DTMF tones on to an audio conferencing bridge or to another MCU where a conference is cascaded.

It is most likely that the RMX Gateway is incorrectly negotiating the DTMF support. This should allow the DTMF to work.

Iain Buck

TME, Cisco Telepresence Solutions