Each WRC repeater site has two tones ... Raleigh uses one to talk "to" field units, and field units use the other to talk "back to" Raleigh.
When field units go to talk-around to talk to each other, they use the dispatch tone (186.2 Hz in the case of the Concord site).
From my listening over the years, Raleigh dispatch generally does not monitor the talk-around side of the repeater, but has the ability to do so on atleast some of the sites.
By having two tones, the dispatchers in Raleigh can focus their attention on listening for field units calling them, rather than having to hear all communications going on at each of the repeater sites.
Here's some of the pairs of P.L. tones in use at sites:
Forest City - 159.090 .......... 203.5 and 136.5
Winnabow - 159.285 .......... 173.8 and 136.5
Mount Mitchell - 159.285 .......... 186.2 and 210.7
Lumber Bridge - 159.315 .......... 151.4 and 136.5
Concord - 159.315 .......... 186.2 and 151.4
Haw River - 159.315 .......... 210.7 and 203.5
Boone 159.345 .......... 186.2 and 103.5
Troy 159.345 .......... 173.8 and 151.4
Winston-Salem 159.345 .......... 203.5 and 210.7
( the first tone is used by dispatch, and by field units for talk-around; the second tone is used by field units when talking with dispatch )