fault code?

hi we had a power cut recently but when power was turned back on i keep having a code saying pt when i put my alarm code in the system alarm goes off. i have only had this alarm for a few years and no longer have the booklet to find the problem i think the ststem is a get alarm but there is no writing on the alarm i cant afford another alarm at the moment and would be very appreciated if you could tell me what to do next thanks regards ian