Here are two threads that might be of help.
http://www.picbasic.co.uk/forum/show...hlight=voltage
http://www.picbasic.co.uk/forum/show...hlight=voltage

But... if all you are wanting to do is see if the signal is HIGH or LOW-- ON or OFF--and the voltage IS only 22 VAC. A rectifier to change to DC and a voltage divider to bring it down to 5 volts should do the trick.

If the high voltage was greater than 32 to 48 volts I would recommend a transformer for the voltage drop along with a page full of safety precautions.