Installation of dual TOR-940 ATC/MODE-S/ADS-B Transponders Sikorsky S-76C STARTING ENGINES BATTERY OR EXTERNAL POWER 27. Avionics — As desired. a. Transponder (RTU-4200)— ON. b. ATC FLIGHT ID(s) — Verify correct. c. ADS-B 1 FAIL Annunciator — Verify ADS-B 1 FAIL annunciator is extinguished. d. ADS-B 2 F