Montgomery County has APEX radios in place in all stations along the border and I believe most stations in the county, so they can operate on the TDMA only talkgroups (G and H zones). Any other mutual aid companys at this time do not have the radios so they must stay on the dynamic talkgroups (Zones A, B, C, & D). The dispatch printout gives the talkgroup to respond on in the information on the incident.
When there is an incident on talkgroup 3 or 7the incident commander also has additional talkgroups he/she can use without asking for permission. Example: incident on 8A3, the incident commander also has 8A4, 8A5 and 8A6 that they can use. Talkgroups 11 and 12 does not have additional talkgroups that are automatically attached to the incident or in other words, they can't be "expanded".