A sensing circuit is useful with a power outlet and a power tool having power supplied thereto via the power outlet. The sensing circuit includes a generator, a transmitter, and a detector. A first signal having a high frequency is developed by the generator and supplied to a first terminal of the power outlet by the transmitter. The detector is coupled to the second terminal of the power outlet and tuned in accordance with the high frequency to develop a second signal indicative of whether the power tool is coupled to the power outlet. The sensing circuit may be used in conjunction with a regulating circuit and a two-position switch useful for controlling the electrical energy supplied to the power tool and a vacuum cleaner having the power outlet disposed thereon.