I just have an inquiry about q16 on page 139 of the irex text book, about mode C transponders. The question asks what a mode c transponder has the capability to transmit information on. The answer the book indicates as correct is that it transmits information on position and height, but this doesn't match with my understanding.

I believe that all a mode c transponder can transmit information on is pressure height and the 4 number squawk code. The position is then determined by the time difference between the interrogation transmition from the radar head, and the time it takes to receive the pressure altitude and 4 digit code reply from the transponder. This raw information is then run through a multi track processor and qnh processor which then plots the position and level on a eurocat display screen. It is only when you get a mode s transponder that the position itself is actually transmitted by the transponder. I believe that in the way this question was actually asked the correct answer should be that it transmits pressure altitude information. Could I please get a clarification on this answer?

Hi Ian,
Agreed, the wording on that could be tightened up. Only mode S transponders actually transmit position information (and a squitload of other data too). Thanks for the feedback!
Cheers,
Rich