In the Nikon FA repair manual it is stated that the lens speed is compensated when an (AI-S) TC sets the Focal Length Signal Switch to its innermost position (B=0, A=1).
It makes good sense to compensate the maximum aperture when a TC is mounted. Otherwise FA or F4 will require a higher EV before they ignore the meter segment (standard is 16 1/3 EV) with evaluative multisegment metering. There is however a difference in one f/stop between mounting a TC-14A, B or C compared to a TC-201 or TC-301 - but there is only one TC setting of the Focal Length Signal Switch!
The question is: Will the compensation be one or two f-stops? - and does the 2* TCs and 1.4* TCs engage the same way?
The FOCAL LENGTH INDEXING RIDGE of a TC-14B is slightly more protruding than the Focal Length Indexing Ridge of a NIKKOR 400mm 1:3.5 implying that the engagement with the FOCAL LENGTH INDEXING PIN could differ between a long lens and a 1.4* TC. It is however difficult from fig. 8-2 to infer how much they must differ (the repair manual of 400mm 1:3.5 says the FLIR must be within 7.85+-0.15 mm from the mounting base).
It is a mystery why Nikon decided to solve the relay of the actual resulting maximum aperture this way (by means of a Focal Length Signal Switch) instead of letting the mechanical relay of the TC take care of it.
To see what the lens side looks like there got to the FOCAL LENGTH INDEXING RIDGE.page.
| Lens or TC | A | B |
| 105mm or shorter | 1 | 1 |
| 135mm or longer | 0 | 1 |
| TC-14A, TC14B, TC-201 or TC-301 | 1 | 0 |
1 = open