Abstract: In one embodiment, the amount of power delivered to a load depends upon the length of time a touch switch is actuated or on the number of times it is actuated. In a second embodiment, the power delivered to a load starts at one level and smoothly changes to a second level. Both embodiments include a zero-crossover detector, an a.c. operated load, and a circuit responsive both to zero-crossover pulses and to a circuit actuated by the touch switch for controlling the portion during each half period of the a.c. during which power is applied to the load.

Abstract: a gate-turn off silicon controlled rectifier (GTO) is operated by selectively applying to the gate electrode thereof one of: (a) pulses of a polarity to turn on the GTO, (b) pulses of opposite polarity to turn off the GTO, and (c) pulses of alternating polarity to successively turn the GTO on and off. The pulses are derived from a circuit which includes a capacitor, an AC source for charging the capacitor in opposite senses, a diac circuit responsive to a charge of greater than a given amplitude, in either sense, stored in the capacitor, and a switch circuit for selecting from among the pulses produced by the diac circuit one of a, b and c.