Glen Akins (@bikerglen) writes about this clever vintage indicator project on the Photons, Electrons, and Dirt blog:

Relive Your Best Mountain Bike Descents on a Vintage Aircraft Altitude Indicator

In this project, I use a Python script and an updated version of my digital-to-synchro project to replay my mountain bike climbs and descents at 60x real time speed on a vintage aircraft altitude indicator. The updated D2S converter fits on a single board and uses three Microchip MCP4802 DACs and three TI OPA548 power operational amplifiers to produce high-power 400 Hz AC waveforms to power and control the servo loop in the altitude indicator.