Software PBX¶

Several software-based phone exchange systems are available with ISDN support.
Interfacing to hardware is often possible through multiple interfaces (mISDN, DAHDI, etc.)

We're focusing on the modern DAHDI (formely known as Zaptel) here.

Asterisk¶

- Signaling works fine (E1 PRI, S0 BRI, routing between them)
- Voice calls work fine
- Data calls have the correct signaling, but data corruption

Yate¶

Patched version (https://gitea.osmocom.org/retronetworking/yate)

- Signaling between 2 E1 PRI lines defaults to 3.1kHz audio, data bearer cap seems to get lost (partly patched)
- Voice calls work fine
- No native overlap dialing support (overlapped.php offers a workaround, questionable quality.)

FreeSwitch¶

Patched version (https://gitea.osmocom.org/retronetworking/freeswitch/)

- Trouble with bearer capabilities as well, needs patches
- Voice calls work fine