TC reported smoke external alarm at car1507. Rear T204 conduct a line clear and confirmed no heat a nd smoke. Staff(KTB) checked and confirmed no heat and smokeon exterior and interior of train. ~~~~~ 1627 TC reported smoke external alarm. Rear T204 conduct a line clear and confirmed no heat and smoke. Staff(KTB) checked and confirmed no heat and smoke on exterior and interior of train.  1627 FC 723 (Fire external} Put 'Smoke External' to cut-out & removed SDR11 relay in the fire control panel. Isolated/tagged. Checked & confirmed SDR11 relay in fire control panel faulty. Isolated & removed. Shortloop to BSD to check smoke detector.  Ashvin 44987 RSD Check & replace smoke detector.Surrounding area are dry.Function test ok.Also replace smoke detector relay #1627-smoke detector:- Not: 2467637 raise to CSC Done by Imran/Faiz.  04/03/23