Which device is typically used to set a numeric address for a PLC in the field?

• A. Indicator lamp
• B. Pushbutton
• C. BCD thumbwheels
• D. Toggle switch

Answer: (C)

Setting a numeric address in the field needs a device that can input and hold a precise multi-digit decimal value. BCD thumbwheels provide a separate wheel for each digit, so you can set each place (ones, tens, hundreds, etc.) to the exact number you want and the value stays put until you change it. This direct, stable input matches how PLC addresses are written and read. In contrast, an indicator lamp only shows status, a pushbutton is momentary and won’t store a number, and a toggle switch is limited to two states, which isn’t practical for multi-digit addresses.