How can I mend my Scantronic 9454 Home Alarm system?

Scantronic 9454 Alarm Control Unit 5 Zone. Its circa 30 years old and has not been maintained for 15 years.

Alarm keeps going off and Fault Service System lights come on. Entering the code the pressing "Enter" stops it but its triggering within minutes of doing this.

How can rectify this or I switch off the alarm totally? Many Thanks. Mike