On my 69 Chevelle. Where the master cylinder brake lines connect to one fitting on the frame below steering column with an electrical connection in the middle. How does this block work? Are the 2 lines seperate in the block or are they joined together internally?
What is the electrical connection for?

That little junction block serves two purposes. It has an internal valve which "senses" unuequal pressure between the front and rear systems and activates your emergency brake warning light if there is. When the pressure between the two systems is equal, the little valve remains centered. If one system loses pressure, the valve/switch is pushed to one side, activating the warning light. That's what the electrical connection is for. The second function is, of course, to provide a place to connect the two systems so this warning system can function. On a vehicle which has front DISCS and rear DRUMS, the block is replaced by a proportioning valve which actually controls the amount of pressure reaching the rear brakes. It also serves as a brake failure warning device, lighting the brake light if either front or rear system fails.

Thanks Front disc rear drum. The car had roll controll, proportioning valve, then distrabution block Should I still run this system? It worked good. I am rerouting things to clean up firewall and motor bay.