If it has a clock chip and alarm function, then that is the possible “detonator”. If the demonstrator alarm panel has remote RF capability, then the options increase a lot.
The presence of the transformer and power cord really means nothing — just convenience. Just go upstream past where the incoming AC gets rectified to DC and that’s where you put in the leads to a battery pack.
This isn’t STEM curiosity or innocence. It was planned for a campaign/lawsuit.
I understand that. However, take a look at it: it’s the guts of a cheap digital clock, with no apparent modifications. It doesn’t even have the 9v backup battery connected; i.e., it can only operate when plugged into the wall.
There is nothing resembling a blasting cap or detonator, and nothing resembling an explosive. No stray wires leading anywhere suspicious. It looks like what it turned out to be: the guts of a digital clock stuck into a case.