Event Detail

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{
    "id": "cc16de00-c31f-5c44-a34a-615e6beba883",
    "kind": "official",
    "name": "FeTAp 611 unplugged: Taking a rotary dial phone to the mobile age",
    "slug": "fetap-611-unplugged-taking-a-rotary-dial-phone-to-the-mobile-age",
    "url": "https://api.events.ccc.de/congress/2025/event/cc16de00-c31f-5c44-a34a-615e6beba883/?format=api",
    "track": "hardware",
    "assembly": "ccc",
    "room": "62251a07-13e4-5a72-bb3c-8528416ee0f2",
    "location": null,
    "language": "en",
    "description": "There are people who throw away old telephones - and then there are those who find them in the garbage and think, „How can a microcontroller actually read the digits from a rotary dial?“\r\nThis talk follows the journey of transforming a classic German FeTAp 611 rotary phone into a mobile device while keeping its vintage charm. Building on earlier retrofits, this project aims to combine the following design goals into a mobile version of the Fernsprechtischapparat:\r\n\r\n- Grandparents-compatible – The phone shall be easy to use by non-technical people, showing the same look and feel as the original phones, including details such as a dial tone.\r\n- easy phone switching – Switching between FeTAp and regular cellphone shall not require unscrewing the phone to switch SIM cards.\r\n- standard components – PCB/PCBA suppliers shall be capable of manufacturing boards at a reasonable price.\r\n- device-agnostic circuit design – Adapting to different phones (e.g. W48, FeTAp 791, FeTAp 611) shall minimize the need for changes in the schematic. This includes a ringing voltage generator that shall be powerful enough to drive an old W48 phone.\r\n\r\nThis talk will walk you through certain aspects of the German analog telephony standard 1TR110-1, and the challenges faced when implementing those on a battery-powered device with little space. It explains\r\n- the state machine implemented on an STM32 microcontroller,\r\n- how to connect old carbon microphones to modern audio electronics,\r\n- designing (and avoiding mistakes in) a flyback based SMPS to generate 32V - 75V ringing voltage,\r\n- how to generate 25 Hz AC using an H-bridge,\r\n- and how to layout the PCB such that the ancient second handset connector can now be used for USB-C charging.\r\n\r\nIn the course of the development, I discovered that the project is not only a good way to get a glimpse into various aspects of ancient and modern types of electronics - but also into people’s reactions when such a phone suddenly starts ringing on a flea market… :-)",
    "schedule_start": "2025-12-27T12:50:00+01:00",
    "schedule_duration": "00:40:00",
    "schedule_end": "2025-12-27T13:30:00+01:00"
}