Abstract: An electronic circuit device includes a metallic member composed of a thermally and electrically conductive material and comprising a unitary mass defining a heatsink and being free of mechanical or electrical transition joints. Electronic switching devices are mounted on the member and in electrical and thermal contact therewith. A control circuit and a conductor are each mounted on the member and adjacent the switching circuit devices and electrical conductors interconnect the switching circuit devices with the control circuit. The control circuit and the conductor are thermally and electrically isolated from the metallic member. The metallic member comprises a heatsink for the electronic switching devices and a conductor for currents being switched thereby.

Abstract: The variable resistance speed control switch for a power tool has a wiper which slides over a resistor which has a non-linear resistance curve matched to the motor. The resistor is made by thick film technology and has a ceramic substrate covered by 950.degree. C. glass and fired to give the substate a glass smooth surface. Then a 100K ohm ink is applied in a pattern designed to give a non-linear resistance curve tailored to the performance of the motor. A resistive termination is provided to diffuse the power concentation under the stationary contact. A 1 meg ohm ink covers the 100K layer and part of the terminaton. The 1 meg ink contains a lot a glass which fuses and flows out when fired. The 1 meg ink will flow out to the same glass smooth condition as the glass bottom layer. The wipers are not subject to much abrasion or wear.