Europa-List: Tacho wiring?

[Richard <riddon@btinternet.com>]

Hello the new forum!

Can anyone advise me which wire goes where when connecting up the tacho on a
912S?  There are three terminals on the back:- 
1+,  2-,  and 3.  There are two wires coming from the engine, white/yellow &
blue/yellow.  

Neither the Rotax manual nor the factory wiring diagramme are very clear as
to what goes where.

Cheers,

Richard Iddon. G-RIXS (XS tri builder no 533)