Videoconfrencing/telehealth Info

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I know the basics but does anyone know of a good resource or have a good course on videoconferencing/telehealth.. I have to write a test on it next week and and trying to find some a more technical guide to go though..

something that goes over all the components (gatekeeper, end points, bridges, codecs ect)

Let me know if anyone knows of any!

Thanks guys!