The invention relates to a step switch assembly which switches power on and off in a stepwise manner in dependence upon the upper and lower limiting values of a control signal. The switch assembly may be used for operating in a stepwise manner a bank of units such as motors wherein each motor, or group of motors, represents a portion or part of the total available capacity of a system such as air conditioning system. The step switch assembly includes a reversible counter, a transmitter for sending digital impulses to the counter, and power stages which are switchable on and off in dependence upon information stored at the counter output points.