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Playlist "37C3: Unlocked"

Analog rotary phones get a second life with raspberry pi

Hans Gelke

An open source project involving an automated telephone exchange powered by Raspberry Pi, utilizing old rotary phones. The system imitates exchange setups from different countries across the globe, allowing users to feel the genuine experience.

Rotary-dial analogue phones were once a necessity, but now they lay dormant on shelves or tucked away in attics. This is largely due to the replacement of traditional landlines with fibre-optic modems, rendering analogue phones obsolete.
In addition to their sentimental value, rotary dial phones provide several advantages, including reduced electrosmog emissions, protection against eavesdropping, repurposing outdated technology, and promoting a slower pace of life.
The contribution explains how to build a private telephone exchange for eight people using rotary dial phones. The exchange is powered by a Raspberry Pi and custom analogue electronics. The following themes are covered:
- The construction of a PBX which resembles telephone exchanges in various countries worldwide, giving users a realistic experience.
- Handling of call initiation, routing, full duplex voice transmission and human-machine communication.
- The software implementation on the Raspberry Pi running Linux.
- A study of enhancing the open-source software with additional functionalities.

Due to the readily available Raspberry Pi hardware and software programmability, this project invites everyone to participate.