TIMS Pre alarm RDT smoke external. Staff(BSH) checked no smoke . Reat T 212 line clear - ok. TIMS Pr e alarm RDT smoke external. Staff(BSH) checked no smoke . Re at T 212 line clear - ok. ~~~~~ 2511 TIMS shows Pre alarm smoke external. Staff(BSH) checked no smoke. Rear T212 line clear - ok. CE checked 2511 smoke external pre-alarm able to reset. No abnormality. Depot 2511 smoke external operational check.  2511 Found FC 721 (smoke external) on TIMS. Checked #2511 external smoke detector. Found smoke detector unit, plaseal, cable gland and gasket - OK. No water or dust ingress. Swapped SDR11 relay on fire control panel between #2511 & #1511.  Aliff/Redzwan 45174