Just like at this very event (39C3), the last few years a small group of volunteers has delpoyed and operated legacy telephony networks for ISDN (digital) and POTS (analog) services at CCC-camp2023 and 38C3. Anyone on-site can obtain subscriber lines (POTS, ISDN BRI or PRI service) and use them for a variety of services, including telephony, fax machines, modem dial-up into BBSs as well as dial-up internet access and video telephony.

These temporary event networks are not using soft-PBX or VoIP, but are built using actual de-commissioned hardware from telecom operators, including a Siemens EWSD digital telephone exchange, Nokia EKSOS V5 access multiplexers, a SDH ring for transporting E1 carriers and much more.

While some may enjoy this for the mere hack value, others enjoy it to re-live the digital communication sear of their childhood or youth. Howevre, there is a more serious aspect to this: The preservation and restoration of early digital communications infrastructure from the 1970s to 1990s, as well as how to operate such equipment. As part of this effort, we have already been able to help communications museums to fill gaps in their collections.

The talk will cover

• the equipment used,
• the network hierarchy we build,
• the services operated
• the lessons learnt
• newly-written open source software for interfacing retro telcommunications gear