payphones.telesfor.org
Changes need to be done to the standard keypad assembly in order to work correctly with the Olympian 5501 controller pictured below, as documented by Elcotel, 1987. Standard keypad may work to some extent, but it usually fails once the voice prompt is to be played. Unfortunately, no instructions (yet) for the APC and other type keypads.
NOTE: TB2 is located on the back of the keypad.
TT = Touch Tone (keypad)