The DC direction changes by one SPST switch(off/on). The left is CMOS(Using MOS-FETs) and the right is TTL(using Bi-Polar Transistors).
LED RESULTS
RED-----POSITIVE(+) DIRECTION ORANGE(LEFT)-----CMOS VERSION
BLUE---NEGATIVE(-) DIRECTION GREEN(RIGHT)------TTL VERSION
CMOS is more efficient and simpler than TTL.
