I have a Optima alarm system which was installed around 15 years ago?

I have a Optima alarm system powered by the mains with sensor points around my home which was installed around 14-15 years ago. a couple of days a go i experience a power blackout for around 30 seconds which affected my alarm were the power is on but whenever i try to activate the system with my personnal code it will not respond? I do not have the orginal manual and was advised by an electrician that either the battery has gone or the system needs resetting with the orginial coding then for me to re-enter with my own password.? can you help