Below is more detailed information concerning the millivolt natural gas combination safety valve. The only wiring diagram I could find is attached to the valve. You can see it if you click on the image above.
For millivolt systems. Manual gas valve with automatic safety pilot. Mounts in any position except upside down. Inlet conn. 1/2, Outlet conn. 3/4. Capacity BtuH 240,000. Includes reducer bushings, LP adaptor plate and built-in regulator set at 3.5 W.C. Specifications: Electrical rating: 250mV to 750mV, pressure tap 1/8 NPT and pilot outlet 1/4 tubing. Optional side taps.