Denver Fire dispatch is now transmitting the 'Vocalarm' station alerting on the Denver Public Safety Trunk System, on TG 07-067 (decimal 951). Station alerting is normally not heard on the main dispatch channel (TG 06-021).
This makes it easy to monitor DFD for calls being dispatched without listening to all the other traffic (if that's what you want), or to listen to both alerting and responses on the trunk system.
The alerting traffic is simulcast on 154.07 mHz, (PL 103.5), along with the dispatch talkgroup, which makes it pretty busy.
The Vocalarm is a system which allows dispatchers to dispatch stations, and make announcements to any or all stations, similar to a P.A. system, separate from the main dispatch channel.