Toucey and Buchanans' interlocking mechanism was more cumbersome and less sophisticated, and so was not implemented very widely. Union Switch & Signal bought their company in 1882.

As technology advanced, the railway signaling industry looked to incorporate these new technologies into interlockings to increase the speed of route setting and the number of appliances controlled from a single point and to expand the distance between the controlled appliances and the point of control. The challenge