TIMS showed Smoke External Alarm at Front M1 car 2609. Staff(YCK) checked and confirmed no signs of smoke / fire / burning smell on exterior or interior of trai n. Rear T260 line clear and confirmed no abnormalities. ~~~~~ Checked and found smoke external. FC 721. Replaced external smoke detector and function test-ok. Security check-ok. #1609 smoke external c/o: Notification no: 2575384 Done by: Saini