Abstract: The present invention relates to a switching device for use in a series loop circuit, and more particularly to a switching device for uncoupling defective circuit components from the series loop circuit, for conducting quick trouble-shooting procedures to locate breaks or shorts in the circuit, and for enabling efficient preventive maintenance programs of the circuit components in order to keep them in good repair, with minimal shutdown time of the circuit or interruption in the supply of power to remaining circuit components. The device according to the invention includes a multi-position selector switch which permits in-situ testing of the circuit components so that down-time of the circuit is significantly reduced, and ease of maintenance is enhanced.