The three components of a photoelectric sensor are the transmitter, the ______, and the contacts.

• A. Receiver
• B. Amplifier
• C. Controller
• D. Detector

Answer: (A)

In a photoelectric sensor, the beam path is created by a transmitter and a receiver. The receiver is the part that detects the light from the transmitter and converts it into an electrical signal, which then drives the output contacts. That’s why the missing component is the receiver—the counterpart to the transmitter that actually senses the light.

Amplifier or controller aren’t the standard name for the middle component in this three-part description, and detector is a broader term that doesn’t fit the common labeling as neatly as receiver does.