It’s apparently a Honeywell sales demo kit.
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.