On the OR946 selector, there was a switch which included TAC and DL amongst its 4 functions. The others being ILS and I can't remember what the basic one was - 'compass' or something?
The 'TAC' position used the offset TACAN box (Folland's gift to every Gnat student) whereas the 'DL' position (which was intended to be for data link on the Frightning, but I don't think was ever actually incorporated) was for 'raw' TACAN which didn't go through the offset box.
Hands up which Gnat students didn't at some stage find themselves in the wrong place through a TAC/DL switch pigs.....??
No Data Link on the Buccaneer - just words of encouragment/abuse from the back!