Question: How do I wire a Tekmar to the Magna using a Tekmar to control a signal from the boiler?

Answer: You will not need a separate control device to do so. Run the wire from the boiler directly to the digital input to start and stop the pump. It is the one marked S/S and the other looks like an upside down T.

If no external on/off switch is connected, the jumper between terminals Start/Stop (S/S) and frame (upside down T) should be maintained in place. This connection is the factory default setting.