Shown for the sub-block adjustable DC power supply. Mainly in the power of three-terminal adjustable regulator LM317 at the core, terminated in the adjustment of LM317 are adjustable potentiometer W, resistor R3 ~ R10 and nine blocked toggle switch S2 and the transistor VT, by adjusting the S2, the output 9-block available in different fixed output voltage. VT is to prevent transistor S2 in a temporary break in the toggle or bad, causing the output voltage is too high and damage to the load. R3 ~ R10 the resistance for reference only.