None of them had provision for battery power ...
Powered with either 240vac into small SMPS board or 240vac/6vdc wall wart.... ...
Problems were mostly poor solder joints although a couple with onboard SMPS had a blown chip. Identical board in both cases; same chip blown;
There were no recognisable markings on the soot, so I replaced whole board .. ..
I bought 11 units and repaired 9 of them with PSU problems; the other two powered OK but had a problem within the operation of the processor system .. .. I could track a signal in but the processor board is all SMD into a 64 pin IC about the size of my little finger nail .. very difficult to follow, so I put the useful bits in a box andthe rest in the bin !