Environment 1: The white USB port supplies power. The black serial plug connects to the cashier counter. The black serial receptacle connects to the serial printer.
Environment 2: The white USB port supplies power. The black USB plug connects to the cashier counter. The black USB receptacle connects to the USB printer. The black serial receptacle connects to the cashier counter. The black serial plug connects to the customer display.
Environment 3: The white USB port supplies power. The black serial receptacle connects to the serial printer. The black USB receptacle connects to the keypad.