Most optical (or photoelectric) sensors do not include the industry-standard notation of “normally open” or “normally closed,” as we would find affixed to every limit switch, push button, selector switch, and most other discrete sensors. Industrial sensor applications face challenges of digital or analog, NPN or PNP, normally closed and normally open, but for optical sensors, the terms “light-on” and “dark-on” must also be understood. These terms describe the default state of contacts in switches, relays, and contactors when no external force or power is applied. USB Mini-Type B Port The USB console port uses a USB Type A to 5-pin mini-Type B cable, shown in the following figure.