A few corrections; They no longer refer to the areas as districts; They are called Troops. Such as Troop 3 Chicago dispatches multiple other Troops such as Troop 2 (Elgin), Troop 5 (Joliet, actually located in Crest Hill), and a few others.
ISPERN is called PRIORITY ONE, not just “priority.” Sometimes if Troop 3 broadcasts a flash message on ISPERN, the Troop dispatcher may say, “Troop 3 Chicago clear ISPERN, KSB242.” Majority of the time, the dispatcher will say, “Troop 3 Chicago clear PRIORITY ONE.” No callsign even though they were multicasting on Starcom21 and ISPERN VHF.
Also the previous person mentioned a few low band frequencies that were used prior to the implementation of Starcom21. They were not using duplex, rather they utilized “split simplex” mode. If it were duplex, both the dispatcher and the car could talk at the same time and not unkey waiting for a response. Sort of like talking on the telephone.
When a Troop 2 unit calls in, he or she says, “Chicago 3 2-27 (if the car is 2-27),” or a Troop Chicago car calls, “Chicago 3 427. Sometimes Troop 3 Chicago specific units are 100, 300, and 400 units. You’ll hear “Chicago 3 121,” or Chicago 3 333.” It was very confusing until it was fully explained to me.
Let’s not forget as of January 1, 2024, all tollway troopers will be dispatched by Troop 3 Chicago. Plus their car numbers *may* change away from their traditional 15-xxx vehicle & license plate numbers. “Stay tuned,” and enjoy listening while you are able because ISP will go encrypted some time in the near future. The Tollway dispatchers will still handle maintenance and HELP vehicles when the transition takes place.