OK, I am NOT a "phoneman", so I don't qualify as an authority on what requires a "phoneman's" expertise. I'm a data guy. Not who contracts out, a captive one, working for a manufacturing company. We've got almost twice as many computers as phones, lol.
I can qualify as an expert on what we DIY'ers think that we can do. We can find out damn near anything on the internet. Copy/paste this: "primary secondary colors cable 25 pair" into google and see what you come up with.
So it's not just that we can get any hardware we want, we can get the information we need, too.