I believe you are referring to audible tones transmitted on the same voice channel frequency as fire dispatch. So, yes, you will hear the tones on the same dispatch frequency, but while you may only hear the tones, the only thing that will tell you they are activating the sirens (and not something else) is right after you hear the tones being broadcast the sirens will activate. (The sirens are probably programmed to run for a set amount of time and shut down automatically.) They also use audible tones to unlock a container on fire apparatus where they store the master key to the lockboxes on commercial buildings. (While they may not be doing this in your local, it’s very common among FD’s.) This way the FD doesn’t need to carry a multitude of keys to unlock each business. They simply ask dispatch to unlock the container on board the apparatus and retrieve the master key that fits all the lockboxes on the wall of the commercial building or the fence lines around an industrial complex, located at the gates. It’s just a way of keeping secure the master key. Dispatch will record each time any apparatus box is accessed and request notification when the master key is returned to the same lockbox.
I don’t want to hijack this thread but the SR30C touts a 500 channel capacity as one of its major selling points. It strikes me as odd why that would be anything but overkill. Who would have a need for that many channels in a simple analogue only receiver? True, the price is cheap at around a $100 but I see it as a teaser radio. Once you get one it won’t be long before you realize there’s a lot more that it won’t receive! Of the reviews I’ve read, the major selling point seems to be the 500 channel capacity, much of which will never be used. Do your shopping wisely… first check what it is you want to hear and then choose a radio that will accommodate those choices.
