It sounds like the engineer has programmed it for engineer reset on tamper (usually to protect him from you tampering with a system under a contract). If you post the code here I will post you an anticode for it. Alas if its a tamper fault thats causes it to activate again you will need another anticode (different each time) Remedy - call in an engineer - fix the tamper fault - disable the engineer reset on tamper option.
Alarm Engineer Bristol
October 2007