Simplified speed control for single phase locomotives

A GREAT number of locomotives have up to this time been equipped with control systems utilizing either electro-pneumatically or electromagnetically operated unit switches and preventive coils in various combinations. However, a great many single phase locomotives built abroad have been equipped with a simple and quite efficient control system, whereby a tapping switch and bridging resistances are used. With such a tapping switch the number of current breaking switch units is greatly reduced. The weight of the entire control system, which does not utilize any preventive coils, is also less than that of unit switch-preventive coil systems.