Abstract: A vital switch control circuit for a railroad switch machine includes a permanent magnet motor which is immune to stray or induced a.c. currents, and which is operable to either of two directions depending on the polarity of energy applied thereto. Switch-normal and switch-reverse contacts of a switch request relay logic circuit establish alternate positive and negative-current paths which are connected over a minimum number of line wires to a motor control contact arrangement and to a mechanically-interlocked, dual-coil, reversing contactor. The reversing contact is operable only above a specific d.c. voltage, therefore providing low-level d.c. immunity in case of grounding or cross-over conditions arising in the line wires. A reverse motor contact and a normal motor contact are used to alternately establish negative-current paths to the permanent magnet motor.