How can I unfreeze the key pad please Optima XM?

I cannot key in my number in order to set the alarm so not been used for some time. It is stuck showing the attack and power light showing. It is on a ring main on its own - can I shut off the power then put it back on (and assume then the alarm will ring loudly and then need the number putting in and then press set set - OR NOT please? Thank you.