Self-Normalling. A self-normalling video jack internally routes a signal from one video device to another. Typically, BNC connectors are used with the rear source (input, Row 1), and rear destination (output, Row 2). On the front are standard video patch ports. The internal normal path runs from the rear source to the rear destination. The signal can be rerouted by inserting a patch cord into either front port. Removal of the patch cord returns the signal to the normal path (i.e., “self-normalled”). These video jacks are available so that, in a patched mode, the unused signal is either terminated to a characteristic impedance of 75 ohm, or unterminated (open circuit).

Dual Self-Normalled Unterminated.
When patched, these jacks route signals straight through with no termination of unused signals. When unpatched, the rear source port is normalled to the rear destination port.

Single Unterminated.
These jacks route signals straight through, with no normalling and no termination.