155.190 was the statewide intercity freq in NC, and the encode/decode system was manufactured by Secode (Sequential Code Device), and no, it wasn't spelled "c-code". A 2805 Hz tone was generated and broken by the cammed contacts of an ordinary phone dial mechanism when you dialed a code. Four digit codes were assigned to each agency that had the 155.190 base stations, and the NCSHP comm center in GSO had the code 0225. If I remember correctly, dialing "6" was the "All Call" number. The early hospital-to-ambulance mutual aid freqs used the same devices.
As a former telecommunicator and then radio tech for the SHP, I can tell ya a bunch about "the old days." The 155.190 base station was then, and still is today, a GE Master Progress Line all-tube 250 watt VHF high band station with the antenna at about 175 feet on the tower on East Market Street. The antenna is toast now, the feedline center conductor foam is probably caramelized by time and lightning several times over, and the SWR is known to be about two gadgagazillion to one, and I think the control lines are no longer connected to the consoles, but the old gal is still on and operating, just waiting for signals that don't seem to come anymore.
And yes, I do remember 39.10, 39.50. and 39.54. Hell, I remember when the NCSHP had one channel. I guess this info really dates me.