TG2 used to be Air and Ground Electronics :- L Fitt GR, LFitt GC, L Fitt AR & L Fitt AC
Then in 77 came the re-org and L Fitts moved to TG3 to eventually become via a very convoluted route through L Tech GR/GC, L Tech AD/AF(R)/AF(C)/AF/TC, ending with Eng Tech EL. I think L Eng Tech AD etc also ended up in the mix somewhere
In the same change L FITT AC/AR became A Fitt AR?AC
AF(R) & AF(C) being interim trades at the start of the split, GR airfield bods became AF(R) until they had done their comms assimilation course and the similar for GC airfield bods and their radar assimilation course.