I'm an Electrical Designer and I would like to learn more about Telecommunications for a building, from the Main Telecomm room to the rest of the building, things like cable size and types, conduit sizes, equipment, etc.

You need to sign up for a college course for it. There is no possible way to cover everything here. Trust me there... I've been in that sector for 30 years. It's a discipline in itself... and takes YEARS to be reasonible knowledgible much less proficient in. And Decades to know inside and out. EVEN with an eletronics Engineering degree. An Electrical Engineer won't understand most of what goes on, its far too different from that discipline.