The NAC92 is connected to the Flatcap via a SNAIC5 (band nearest the NAC) - this provides 24V DC power and takes signal from the pre-amp. Then the Flatcap is connected to the NAP90 via a SNAIC4 (band nearest the Flatcap) - this takes signal from the Flatcap to the NAP90.
To connect your Headline just plug the captive DIN5 into one of the tape in/out sockets on the NAC92.