Hello to all. Thanks to all for your advice, it has helped us go ahead. The step down transformer I got from your sources works well though it measured 123V ac output instead of the 120V ac, but the alarm is working well and the dialer function surprisingly also. I checked up circuit and it seems neither SMPS nor a transformer , but is as Jim Thompson had said that a capacitive reactance with relative circuitry of Zeners , diodes and so forth is used. I am in the act of modifying the circuit board of 1 of the modules to which the radio signal will be transmitted in case of fire and as also this is supposedly powered from 110V I want to change it to accomodate the 232V my mains is delivering. I'm replacing some of the lower voltage components with higher voltage / power components I had some problems in differentiating between a varistors and capacitors but it seems solved. They used the same color , very funny I think.
My supplier sent me some higher watt resistors which are smaller then the originals on the board ... very fishy I think. What do you say?
Hans