-12, -5, 0, +5, and +12 lines come in through the thick black cable. Earth is the separate thin yellow wire. The little PCB supports 3.3v and 1.8v regulators, and the LED and its series resistor (mounted on the rear). The PCB is powered by wires tapping the 0 and +5 lines, then it feeds the 1.8 and 3.3 terminals.
