The Flipper Zero can use the GPIO to output electrical signals and work as a signal generator. I last used this to simulate an antilock braking system module on the vehicle to confirm that each one the wiring and desktops in the vehicle have been working. I use this function https://flipperzeroforsale63452.goabroadblog.com/35324428/the-2-minute-rule-for-lab401-flipper-zero