muehlbronner.de
VoIP · Linux · Software · Hardware
Senior Administrator Telephony at Transdev, previously 17 years with the same telecom provider (42com, later nexxtra), most recently as Senior VoIP Engineer. I have been working with Linux for more than 20 years and run SIP networks with OpenSIPS, Kamailio and Asterisk. On the side I build my own tools: audio analysis, an ad-free video client and ESP32 boards that use radio to sense what happens in a room.
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What I build outside of work: tools for real problems, from audio analysis to radio sensors.
Noise lab
Desktop tool for tracking down a faint tonal noise source at home: microphone FFT and spectrogram, a peak detector with long-term logging, test signals across several Bluetooth speakers and an auto mode that learns and watches tones. It has grown into a lab for speech and video analysis: speaker recognition, emotion, transcription and AI evaluation.
YouTube without ads
App for Windows, macOS, Linux and Android – and from version 0.5.18 on Google TV too: tested on a TCL TV, fully usable with the remote. Flimmer fetches video data directly through YouTube’s internal API and plays it itself, so ads are never even loaded. With SponsorBlock, DeArrow, subscriptions without a Google account, live chat, mini player and signed auto-updates.
Delivery from your own street
Android app that makes food from restaurants without a delivery service available: someone from the neighborhood picks it up on foot, with restaurant and courier within a 500 m radius. Live tracking, ID and selfie checks for couriers, two-way ratings and GDPR data export. By design, the app never handles money.
kiezboten.app (German) →Kiezi live →Clickable prototype (German) →Design & logo (German) →Animations (German) →
Radio as a sensor
WiFi as a sensor: an ESP32 reads the channel state information (CSI) from every WiFi packet it receives – how strongly the signal arrives on each subcarrier. When someone moves in the room, these values change measurably. That makes it possible to detect presence and motion without a camera, even through walls. Plus an ESPHome component that brings the battery of a Fiido Air e-bike into Home Assistant over Bluetooth.
WiFi sensing in depth →Covert radio channel · video →esphome-fiido-air on GitHub →
Physically track down Bluetooth devices
Live radar for Bluetooth LE devices and iBeacons, sorted by signal strength instead of estimated meters. You stand in the center; zones from “very close” to “far” can be dragged with the mouse. Click a device, start walking, and a large gauge says “warmer” or “colder”; when a device enters the “very close” zone you get a sound and a flash, debounced against false alarms. Devices are classified by manufacturer and service IDs, and iBeacons are recognised even after a MAC change. Plus history, an ignore list and a top 10 of the devices that move the most. Runs locally as a single Python script with a browser UI; a native Android port brings it to your phone with background scanning, notifications and vibration.
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More than 20 years in IT operations, 17 of them in telecommunications, focused on VoIP and Linux.
SIP networks and trunks, OpenSIPS, Asterisk, session border controllers, Debian servers.
Data processing and help desk.
Maintenance of operating systems, hardware and software for end customers.
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How secure are this site and your data? In short: there is nothing to steal here – no accounts, no database, no cookies. The server behind it is hardened anyway, because I take this seriously professionally. The figures come live from the server.
Live figures from the server, refreshed every 30 minutes – no IP addresses or visitor data.
Attacks detected in the last 30 days by country of the attacking IP address. It shows where the machines are – often hijacked servers or rented cloud instances – not where the people behind them sit.
origin this server · drag to spin, tap a country to fly there
No cookies, no tracking, no embedded third-party services – fonts, scripts and images come from this server. Access logs are deleted after 7 days. Details in the privacy policy (German).
HTTPS only with HSTS, HTTP/2 and HTTP/3, a strict Content Security Policy with Trusted Types, no embedding in other sites. The light/dark switch keeps its choice in your browser.
A static site without a database, without logins, without PHP – the server only answers requests with files. Flimmer downloads redirect straight to GitHub.
CrowdSec with its community blocklist stops known attackers before they knock; fail2ban and a connection brake in the firewall stop scanners, floods and brute force.
SSH with keys only and rate limiting, services in systemd sandboxes without privileges, daily integrity check of system files, security updates applied automatically.
A rented container at a hosting provider, not my own data center: against attacks that flood the line, only the provider can help. Everything else is craft – and that is done here.
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Questions about a project or interested in working together? Drop me a line.
Kiezi, the bear from the Kiezbote app, waits here with you – just like on the couriers' empty job screen. Every 45 seconds he performs one of his acts; tapping works too. More (German) →