What is a Curtain Motion Detector?

A curtain motion detector is a detector whose detection pattern differs from traditional motions in that it is thin and not expansive. Whereas traditional motions such as the 5800PIR-RES are capable of monitoring a whole room, a curtain motion detector is more suitable for monitoring traffic through a door, or protecting well-defined areas. You might think of them as a product similar to the lazer patterns in spy movies. Taken from the installation guide of the IS216T-CUR, which is Honeywell's most popular curtain motion detector, below are the patterns of detection for the device.

As you can see, it earns its name from its curtain like zones of detection. Like a curtain hangs down as a thin veil on a window, the curtain motion only detects movement that is directly in its thin line of site.