[Asterisk-Users] DTMF skipped when calling from ISDN to SIP...

[Eric Wieling aka ManxPower]

Nicolas FOURNIL wrote:
> Hello
> 
> 	I have done the following test-network:
> 
> 	IP-Phone <=====> ASTERISK <======> ISDN <====> PSTN Phone
> 	(SIP)			   +
> 				  SER
> 
> 
> When I'm calling from the PSTN phone to the IP (SIP) phone:
> 	I cannot get ANY DTMF from PSTN, they seem destroyed by the codec (small
> scratches).
> 	I listen DTMF from IP-Phone (SIP INBAND!)
> 
> When I'm calling from SIP phone to PSTN:
> 	Same result, no PSTN => IP DTMF !

Inband DTMF only works with the ulaw and alaw codecs.  This is not an 
Asterisk issue, it's just the way the other codecs work.  You need 
RFC2833 or INFO DTMF if you want to use the other codecs.