We have recently moved into a house with an Ademco Vista 20 alarm panel.
One of the children unplugged the power supply and the battery has completely drained.
When the power is switched back on, I get the code OC showing in the keypad display.
The unit was installed in 1998 so getting on a bit, and wondered if the old battery could be causing this problem?
Otherwise, any suggestions on how I can get this unit back up and running again?