I have an Optima XL6, if the keypad fails I turn off mains, unplug battery the reconnect all power, if all hell breaks loose - press the anti-tamper switch spring in, key in PROG then your entry/exit code followed by '0' the puts it into test mode*, Close the casing door.
2 is strobe test, 3 is external bell/sounder, 4 is low volume internal, 24 is high volume internal, 5 is walk test for PIR's. Key in '0' after to stop each test routine.
*Key RESET RESET to put the unit back into normal working mode.
Alec, November 2010