What was found
After takeoff, Pilot had multiple warning indications, "takeoff config, landing gear warning horn". Pilot elected to return to airport. When elected to extend landing gear, the gear did not come down. Pilot used emergency landing gear extension procedures to land. After landing, maintenance found proximity switch unit and landing gear switch had failed. Removed and replaced proximity switch and gear switch. Performed retract checks and returned to service.Reference SDR Control #OZIA200243001 for PSEU part information.