The Model 442 Video Subtractor & Video Comparator allows the user to subtract or compare two video images. The unit performs a video image comparison by subtracting the image stored in its memory from the active picture at its input. Comparison (subtraction) of two live video streams is also possible. It is intended for use in inspection, registration, interferometry, quality control, surveillance and other applications where an easily viewed comparison of two video images can be used for decision making or process control.

The Video Subtractor & Video Comparator has two switch-selectable output modes. One provides the difference plus 0.5. The other provides the absolute value of the difference. Additionally, a switch is provided to invert the output thereby showing the reference minus the input instead of the input minus the reference. A "Difference Threshold" control allows adjustment of the unit's sensitivity to differences.

An additional operational mode allows subtraction of each video frame from the previous frame to provide "frog's eye" capability to display only motion in the scene being monitored by the input video camera.