when I made mine donkeys years ago when every one else was using corsa steering columns (chap in the club gave me some good help he will know who he was ) peter then did a slightly different version latter on.
mine works fine with one oscillator feeding both the inputs and I have it set on one frequency with a latching relay on and off. (cant tell you the frequency I used as I don't want to take my oscilloscope to the garage to check.) but it works well and I would not be with out it now .
1962 mini, bedford CA , KR200. morris 1000, mini pickup.several escorts,ford grandad.ford cortina X2 ,astra, SE5A x 2 ,ford focus.