The major German model railroad manufacturers all offered their own system for train control. The Europeans have a different philosophy about model train operations than those from North America. As such, the design of the Rokal train controls reflected the fact that the trains themselves are controlled by signals (either semaphores or color-lights). After 1958, the 00051 Speed Regulator was at the very center of operations.
In many ways, the Rokal 00051 would presage the design of Märklin Digital components, which were first offered in the 1980’s:
In operation, the 00051 was at the center of the train control panel, with a series of different control switches and distribution pieces attached to each side of the unit.