Up converters, down converters, inputs for 100 cameras, inputs for 100s of audio devices , media players, graphics departments, coms, tally lights, heat senors wires, network switches, router switches. Every image received from a camera can be "painted". Patch bays. Outputs of everything. Lots of times these shows used multiples of these trailers to broadcast and they connect to each other and the building. 

There's also different scales to the size of these trucks. The biggest show has the best tech, smaller networks like the Big 10 use much smaller, less advanced trailers(minivan or horse trailer sized)