The TCR series is a very robust design of SCR phase controlled regulated power supply. In an SCR phase-controlled DC Power Supply, output is controlled by modulating the conduction angle of the controlled SCRs. In the TCR Series, input AC is applied to three pair of bi-directionally connected SCRs placed within the delta connected primary of the main power transformer. The Secondary voltage of this transformer is rectified and double L/C filtered to provide a low ripple DC output. Both output voltage and current are sensed and compared against internal references or externally applied control levels so the supply provides either constant voltage or constant current regulation with automatic crossover depending on control level. Additional circuitry provides bias levels, circuit protection and metering functions.