What is a smoke detector that uses a short beam between a light source and receiver called?

The correct answer refers to a smoke detector that employs a focused light beam to detect smoke. In this context, a spot type photo-electric detector is specifically designed to sense smoke particles interrupting a defined light beam between a transmitter and receiver. This type of technology allows for quick vulnerability detection as it can identify smoke presence by measuring variations in light intensity.

The use of "spot type" in the name indicates its targeted approach, as it focuses on a localized area where smoke presence is most critical. This can result in faster and more accurate detection than more generalized detectors. Understanding this mechanism is key to recognizing the effectiveness of certain smoke detectors in specific environments.

Other options may include terms that don't accurately describe the exact workings of the detector. For instance, "beam type sensor" and "beam type detector" can imply a similar function but lack the specific detail of being a 'spot type' which is essential here. Meanwhile, "photoelectric sensor" is a broader term that might encompass a variety of detection technologies, not exclusively connected to smoke detection or the focused beam mechanism used in a spot type photo-electric detector. Thus, the term used in the correct answer accurately captures the specific design and functionality of this smoke detection method.