1.The DTMF # is the terminating character by default, you should not configure anything. Just set MinDigits and MaxDigits.
Note that after MaxDigits, the gateway moves on, it doesn't wait for #, so if necessary, set MaxDigits larger.
2. Cisco's default interdigittimeout is 10s - so you may want to shorten that (it's set as a VoiceXML Property
Name: interdigittimeout Value: 5s be sure to use the time unit 's' indicating seconds, else they assume milliseconds). Again note that as soon as caller enters the MaxDigits, the gateway stops listening, so if caller enters MaxDigits followed by #, the # barges in on the next audio element.
3 termtimeout is NOT supported by the dtmf-gateway, only when you have a nuance speech server. With nuance, it is used to indicate the amount of time after the MaxDigits are entered that nuance should wait for the # from the caller.