Usage of Video Terminations

The application may require the video signal to be monitored while being digitized by the capture card.

A possible way to address this requirement is using the looped-through technique.

The coaxial cable delivering the video signal from the source camera to the capture card is continued towards a video monitor. In that manner, the camera serves both the card and the monitor.

This technique can be extended to distribute a video image to several video recipients. Each device where the video cable is connected in and out to the next one is called a "looped-through connection".

In a Picolo-based system, any video input can be used in a looped-through fashion using an interconnecting "Tee" structure.

Video signal monitoring

There is one mandatory precaution to be considered when using this technique.

Normally, any video recipient device terminates the coaxial line with a so-called termination resistor (valued 75Ω in video technology). When using the looped-through technique, the termination resistor of all intermediate devices should be removed. Only the terminal device keeps the termination.

In order to support the looped-through technique, all Picolo cards offer a way to remove the termination for any selected input.