The T64H PLC assumes an AC transformer is available with center-tap. This is unique only for
T64H-Relay and does not apply to all other PLC models. (This PLC started life as a customized design and that's why it has an "odd" power supply requirement).
You could actually use a 24VDC power supply to power the PLC if you provide a "center tap". You could emulate this by connecting two 5W, 100 Ohm resistor in series as a voltage divider. This form a 0, 12 and 24V power supply can hence can be used to power the T64H-Relay. It is not very efficient in term of energy use since the voltage divider draws 0.12A at all time on top of the current required to drive the PLC.
