Abstract: A programmable control unit for a vacuum cleaning system, such as central vacuum cleaning system. A control unit is programmed after manufacture to execute a particular control program for performing various diagnostic and operational functions including user interface, voltage level detecting, voltage monitoring, current monitoring, user interface, power supply control, temperature monitoring, AC line frequency detection, operation data recording, speed control program selection, expansion bus interface and service tool interface. Power control to the vacuum motor is facilitated by the control unit directly through a triode for alternating current (TRIAC). Manufacturing costs are reduced by producing a single programmable control unit that can be programmed with a control program corresponding to a variety of different vacuum cleaning devices across a manufacturer's product line.