This is a self contained telephone system which uses regular telephones and wire. A two line phone (dispatcher line) runs off of the middle jack while four lines run out of the other four jacks. There is a buzzer to ring the outer phones and they can ring the "dispatcher" phone.
I know many folks use radios but this system is great for those who want to run old school. I worked for New England Central railroad back in the 90"s and when we wanted to deliver cars to Conrail (CSX now) in their yard in Palmer we had to call the yard master in West Springfield. This system would recreate that feel perfectly.

This is the website for those who would like to check it out