Switch off power , open panel ….remove battery ….wait 30s put power back on ….does the alarm activate ? If so enter code or 1234 it may have gone back to factory default ….if so it needs re programming …. Check voltage at battery leads it should be around 13.8v dc ….if so replace battery
ASD is still going on barbot hall ind est Rotherham , they used to have a shop on site but that was years ago , they where mainly security lights and lighting …i very much doubt if they know anything about that device ….
DR series looked like this ….i know because I fitted loads in the late eighties to early nineties , plus look at the video clip screenshot the aritech is in part 4