AE Project phone

[DBCubix]

Hello all.  I have an AE120 Fortress payphone with an unknown system board inside.  This phone came from NE Ohio, the board says GTE Supply, but nothing much else of help.  It also has a daughter-board (covering the "GTE" of "GTE Supply") connected to the coin mechanism.  Any thoughts on what type of a system board this is and how to program it? 

Also, I want to eventually make this a voip phone which introduces another wrinkle.  A usb voip ATA will put out 5V, but this phone needs 24V?  What would be a good way to connect a transformer so as to not fry an ATA?

Any info would be helpful.  Thanks! 

[G-Man]

 Contains a SmartBoard manufactured Contract Data Company for GTE's COCOT payphones. Doubtful you will find programming information but you can check with one of the COCOT suppliers to see if they have access to the proprietary programming software.

[dsk]

Not sure at all, mine is documented here: http://tinyurl.com/l7yvet3

5 volt in off hook state are pretty common.  24 - 60 v in on hook position.

Polarity matters.

dsk