He could mean the DCS codes for the fire ground simplex channels. Typically a system will include a couple simplex frequencies that are not trunked and are used for talk around.
Beafort County, SC is a great example of this.
They use 2 frequencies that are not trunked. One for police and one for fire. Each fire department within the county has its own DCS tone one the fire frequency and the same goes for the police departments.