I think what your saying is your bob wants a 12v high/low, but the switch is 36v? so you need to make a 12v high/low based on a 36v signal?

Im not sure that is the actual problem, but incase it is, perhaps one of these is the kid for the gig?

http://www.alliedelec.com/Images/Pro...S/70214711.pdf

looks like rs sell them?

Buy Linear Voltage Regulators Voltage Regulator; 50 W @ degC; 10 mV (Typ.); 80 mV (Typ.); 60 dB (Typ.) NTE Electronics NTE1936 online from RS for next day delivery.