See Stan Schreier's Controller Design:
http://www.classicrotaryphones.com/forum/index.php?topic=8522.0
3 Slot Payphone Controller - http://oldphoneguy.com/images/WordConv2PDF2.pdf
Another Payphone Controller - http://atcaonline.com/controller.html
If you find any other resources which should be added to this list, pass the info on to me, and I will post it.
Dave