AC line voltage is converted to regulated 12 VDC by varying firing angle of 10-A SCR. Circuit provides reliable operation for AC line voltages between 50 and 140 V. Key element in trigger-ing of SCR is programmable unijunction transistor that provides variable and accurate control of firing time. Developed for use in power supply that uses digital techniques of sample-and-hold switching to achieve high degrbe of isolation between power line and load without using transformer.-J. A. Dickerson, Transformerless Power Supply Achieves Line-to-Load isolation, EDN Magazine, May 5, 1976, p 92-96.