TC reported Smoke external Front DT car.Staff(AMK) checked, no sign of smoke or fire at Front DT ca r. No abnormalities. Rear T224 line clear, no abnormalities.TC reported Smoke external Front DT car. Staff(AMK) checked  ~~~~~ 3522 TC reported Smoke external indication. Staff(AMK) checked, no sign of smoke or fire at Front DT car. No abnormalities. Rear T224 line clear, no abnormalities. CE 3522 smoke external pre-alarm fault. SDR11 lit. Check no abnormality n reset fault cleared. Depot 3522 smoke external check.  FC 721: Smoke External. Check and found smoke external cable gland missing, no signs of water seepage. Ops20 raised to c/o external smoke detector. Aliff/Daniel/Redzwan 45401 BSD: 3522 TO REPLACE SMOKE EXTER L DETECTOR