Most of the GS coaches in that era had an AV distribution and switching unit made by RiverPark, with a link to a typical unit found at:
https://riverparkinc.com/product/riverpark-avs100hd/
Below is a typical wiring diagram showing how this unit was interconnected. Note that this does not accommodate any HDMI or digital entertainment components, just component analog video and audio.
There are also patch panels used in some coaches to allow connections to be organized in a single panel, like this AVCP101.
AVCP101
Mfg: RiverPark
Description: Audio/Video Connection Plate Features:
- Connection plate allows for better patch cord distribution and cleans up installation
- Allows for better service when you have to service components and put them back
- 4 composite A/V inputs/outputs
- 4 component video inputs/outputs
- Coaxial input from Satellite and output to your TV or A/V switcher
- Audio jack for connection to your audio output from your main TV
Sorry if the image broke...
Chuck