Gardtec 800 system error code -t after power cut?

We had a power cut this morning for all of 5 minutes. In the past, the alarm system has come back on and the LED panel has displayed 'pc' for power cut. However this time, it just display '-t' when the power returned. The LED keypad isn't working as no sound is audible when buttons are pressed. We are moving house soon so I don't really want the expense of repair, does anyone have any idea what's up with it? Sod's law as well, the -t error code isn't anywhere to be found in any manual on the planet!!!