TC reported fire external at Rear M2 car.(Staff)WDL checked no abnormalities. Rear T234 line clear n o abnormalities. TC reported fire external at Rear M2 car.(S taff)WDL checked no abnormalities. Rear T234 line clear no a ~~~~~ 2603 TC reported fire external. (Staff)WDL checked no abnormalities. Rear T234 line clear no abnormalities. CE: 2603 fire external alarm SDR11 able to reset No abnormality  2603 FC 721 (smoke external). Swapped SDR11 from 2603 to 2604 for monitoring. Ops20 raised to check external smoke detector. Justin 45343 BSD: To Check Ecternal Smkoke detector  Replaced smoke external at #2603. Function checked ok. Done by: Arvind/Sufian 22.2.24