Hi, I need a help... I need to build a small system with amateur simplex links with low cost and low power nodes with any PBX functions (gsm trunk, voice menu, mailbox). PBX server based on XIPPR, but may be a Freeswitch too. I need to use only SIP protocol. System programmed using inbond DTMF. Hardware may be a Raspberry pi, with USB soundcard for audio and USB-UART adapter for radio control. Idea is a DTMF control. Any Asterisk app or module need to code and decode dtmf digit (letter) PTT activate with DTMF "A" and deactivate with DTMF "B". For example, node number 2000 connected to node 3000. If to node 3000 audio input comes DTMF letter A (from radio channel), it will activate PTT on node 2000 and letter B will deactivate PTT. One UART pin can be used as PTT, second as CarrierDetect. If CD pin grounded (radio channel buzy) node generate DTMF tone A for activating PTT of second side radio (or radios, if used conference). If CD pin ungrounded, node generate a B tone. This system will be very simple, possible to use different server platforms, gateways, node cost is Raspi 40eur, USB audio and UART is 8eur Same system in Freeswitch tested and works very fine! Could any help with making this addition module? I think, it may be interesting for other voip/roip users Thanks, Mihhail ES1BIS