^^^^ AND how is this accomplished? With the safety valve!
What that says above is the mandate on having the new MC, not HOW it functions.
It is NOT a safety valve... according to the '67 Plymouth maintenance manual its a SAFETY SWITCH. It's actual designation is Hydraulic System Safety Switch. It's description reads as follows: "The Hydraulic System Safety Switch is used to warn the vehicle operator that one of the hydraulic systems has failed. .... As pressure in one system fails, the other system's normal pressure forces the piston to the inoperative side; contacting the switch terminal, causing a warning light to come on in the instrument panel, thus warning the operator of the vehicle that one of the systems has failed and should be repaired."
The switch does nothing other than warn the driver that one of the brake systems has failed. The MASTER CYLINDER provides hydraulic pressure to the other system when either the front or rear system has failed, NOT the safety switch.
