Garage door impulse generator volt free
That's just an odd way of specifying that you should only connect a bare contact closure to the input &mdash; in other words, the device you connect can either pass current between the two terminals or not, and it doesn't supply any voltage or current of its own. In normal use, you'd simply connect a pushbutton switch between the two terminals.

For automated operation, since this is AC, you could use either a relay or an AC-rated optoisolator.