Unlike active infrared systems, it did not require an infrared flashlight.

The infrared optical system also allows users to see in complete darkness.

I can stay low enough for the infrared system to lock onto him.

And Rolodex organizers linked by an infrared system are supposed to be more compatible.

In the early days, there was a continuous infrared system that is no longer in common use.

Ultrasound remained in use until displaced by infrared systems starting in the late 1980s.

Glasses, too, create problems for infrared systems, as they interfere with the light beam.

Night was coming on, and no matter how good infrared systems got, they were never as good as visible light.

Their infrared systems are a lot better than ours.

Here, the theoretically more primitive infrared systems have no problem.