Phone

General

At WHY2025, a DECT and SIP network is operated by the µPOC. Additionally, a fieldphone network is provided by the Chaosvermittlung.

DECT

You can register your personal DECT extension for GAP-compatible DECT handsets at the µPOC Frontend.

Registrations

1. If you've already registered your DECT extension in advance, you can skip to the next section.
2. Sign up at micropoc.de.
3. Go to my extensions to claim your extension.
4. Once done, you can self-register your DECT phone.

Self-register DECT phone

1. After claiming an extension, click the green "PIN" button on the my extensions page.
2. Connect your DECT handset to the DECT network on-site. This usually is called "Register Handset" in the settings of your phone. If prompted for a PIN, use 0000. You don't need to find / touch any base-stations on the field. They're always in registration-mode.
3. On registration, your phone is assigned a temporary number (like "C0123").
4. To receive calls on you claimed number, dial the "PIN" number (from "click the green button) on your phone to bind it to your extension.

You can call other extensions within the WHY2025 network and make free calls to the Netherlands and many other countries.

Not sure if your phone is supported? Check the compatibility list.

SIP

You can register your personal SIP extension at µPOC Frontend. Click the ℹ️ icon next to your extension to view the credentials needed to connect.

SIP Server: sip.micropoc.de
SIP Port: 5060 (TCP/UDP), 5061 (TLS)
Protocol: Use TCP or UDP. TLS is supported, but creates problems with many clients.
SIP Username: <your extension>
SIP Password: <your generated password>

Softphone recommendations

We recommend using Linphone on iOS (App Store) and Android (Google Play, F-Droid).

Linphone uses push notifications to wake-up your phone, when you recieve a call, without draining your battery before you can finish a coffee.
To make this work, you need to enable push notifications in Linphone after adding you µPOC account:

On iOS: In the Linphone-App, goto "Settings", select the account you've already added and enable "Push Notifications" (should be the 3rd slider from the top)

On Android: You first need to enable push notifications for 3rd party SIP accounts:

1. In the Linphone-App go to "Settings", "Advanced Settings"
2. Enter https://micropoc.de/static/linphone-push.xml into "Remote provisioning URL"
3. Click "Download & Apply"
4. Clear "Remote provisioning URL"

This will add sip.micropoc.de to the hidden list of push_notification_domains, which is required for the following to be possible:

1. Open your Linphone account settings ("Manage the profile", "Account Settings")
2. Enable the "Allow push notifications" slider at the top

On iOS AND Android:

• Make sure to use TCP for transport. The push notification parameters will make packets too large for a single non-fragmented UDP packet.
• Don't use TLS either, as audio codec negotiation with DECT phones will probably fail, when TLS is used for signalling.
• Use a pretty long Expire / Gültig bis time setting (e.g. 86400, which is 1 day. Max is 10 days). This determines how long you stay reachable, after your phone suspends the Linphone App.

Test your connection

Dial ECHO (3246) to test your connection. Not provided by µPOC but by a user.

SIP Servers

You can run you own SIP server and connect it to the WHY / µPOC network, using your SIP credentials. Luxim created a woking config for the Asterisk SIP server (Pastebin; No. The credentials in there are not valid and just serve as an example).

Incoming and outgoing calls

• Outgoing call to The Netherlands:

0 <national number incl. 0>

Example: 085 234 2000 → 0 085 234 2000

• Outgoing call to a foreign country:

0 00 <country code and number>

Example: +49 721 266767 2000 → 0 0049 721 266767 2000

• Incoming calls from outside:

Netherlands: +31 85 234 xxxx

Germany: +49 721 266 767 xxxx

(where xxxx is your personal extension)

Phonebook

The phonebook is available here.

Fieldphones

As in previous hacker events, the Chaosvermittlung provides a power-independent, low-tech phone network. Field phones are battery-powered telephones without a dial pad, connected to a central manual switchboard.

To place a call:

• Turn the crank on the side of the phone.
• Wait until an operator answers.
• Tell the operator which fieldphone or DECT/SIP number you want to reach.

Why use a fieldphone?

• They work independently of the power grid—ideal during outages.
• They operate on a separate copper network, unaffected by IP connectivity.
• It's fun!

Ports

We have a limited number of ports (60) on our manual exchange. If you'd like to connect a fieldphone, please send an e-mail to: info@chaosvermittlung.de

Contribute

We’re grateful to the angels who help operate the switchboard—it keeps the network running! Want to contribute another way? Consider recording a voice for the talking clock. Details: [1] Send recordings to: info@chaosvermittlung.de

Further information

• You can use your favorite SIP client with our SIP server. Choose "SIP Account" as the extension type.

If you have any questions, feel free to write us an e-mail: poc@why2025.org

Behind the scenes

• Alcatel OmniPCX 4400
  • Multiple chassis from VH to ACT28
  • Multiple DECT line cards
  • Fiber connections between chassis

• SIP uplink kindly provided by speakup.

Fieldphones Infrastructure

• 2× 30-port manual exchanges
• 2× 4-port DECT uplinks