From 35C3 Wiki
The Phone Operation Center (powered by Eventphone) will be present at the 35C3 this year again with a mobile DECT system and phone infrastructure. After setting up many base stations most of the Messe Leipzig is covered by DECT mobile telephony reception.
You can bring your own DECT phone and register it at the 35C3. So you will be able to call other 35C3 participants for free.
Use the DECT Phone Compatibility List to find out if a phone is known as definitely working or definitely not working.
This year will be the 14th consecutive congress with Eventphone.
This year things have changed a bit. Waiting in line is no longer necessary to register your phone. We have a blog post describing our new registration process. We even made a video for you. Unfortunately, it is in German only.
We have outside connectivity via SIP trunk. PSTN Dialin: +49464438299 < Extension>
It is also possible to dial external German landline and mobile phone numbers. This service can only be used from the DECT and GSM network to avoid abuse.
There will be a GSM network this year see → GSM.
After the Congress
If you don't need your DECT phone anymore after the Congress consider giving it to the POC for organizing future events.
Between Events you can still be connected to us. Register a Number in our EPVPN.