My Deta smoke alarm model 1153 won’t stop alarming,red light flashing all the time,green power light on.have changed battery and performed a reset but still same.As this model is discontinued do Deta have another model that I can use without having to replace all three detectors on the system??

I looked on the Deta website (as you could have done) there is no direct replacement for the 1153. As you have 3 in total I would suggest you change the others too to avoid compatibility problems