There's a compatibility chart on page 2 of this PDF...
http://www.heatweb.com/pdf/Invensys/Programmer%20Compatibility%20Chary.pdf
It does not mention Siemens RWB2E but does show a Landis & Staefa RWB2E which I believe equals Siemens. It shows..
N = Neutral
L = Live
1 = H/W off
2 = C/H off
3 = H/W on
4 = C/H on
I would expect the voltage to be either 0V or 230V (in the UK) depending what the programmer is calling for.
Good luck...
Peccavi, June 2009