External smoke alarm at rear M2. ~~~~~ L3 2527 smoke external fault unable to be reset. Swopped fire alarm from 2527 to 2528 But smoke external fault remained at 2527. Suspect smoke detection unit at No.2 faulty.  Chan SW/Hanafi. 18/05/2020. L3   Replaced 2527 smoke detector set. Conduct smoke test done ok. Done by Kalees/Jun. 19/05/20.