You might be looking at the "National Interoperability" frequencies. If so, in
the early days the I sometimes was used to indicate the 800 channels. Today
you would more than likely see them listed as 8CALL, 8TAC1, 8TAC2, 8TAC3
and 8TAC4. The same is true for the other 2 bands. You will see VCALL and
UCALL as well as the other TAC channel designators.
As to how they are used, in most cases they are intended for mutual aid
communications. In areas where there are a numbert of 800 trunking systems,
you will hear these channels used to allow the different responding agencies
communicate between each other. There may be repeaters set up or they
may be used in the simplex or talk around mode where just user radio to
user radio comms are heard over short distances.
In areas where there is a large use of the UHF channels, you will hear the
UHF interop frequencies. Again most agencies will also program the user
radios to also have the simplex frequency of the repeater outputs.
On VHF, there ar no repeater channels set up. Anything you hear will be simplex operation only.
One good example of these interoperability channels being used was after
hurricane Katrina. There was considerable activity on many of these
interop channels. Many of the normal frequencies were down due to
equipment being destroyed or towers laying on the ground.
The National Guard is just starting to obtain equipment that will enable
them to interface with the local Public Safety agencies. There will be more
interop gateway systems deployed within the guard units as time goes on.
Some real lessons were learned last year after the storms. The channels
that will most likely be used are the "National Interoperability" frequencies.
They will also have their own communications channels and equipment
working on government channels. Much of it will be on the UHF band.
Jim
daleduke17 said:
On the ISP pages it shows different frequencies for V-tac, I-tac, U-tac and the respective call channels. What does the ISP use these channels for? I know U and V are for UHF and VHF, but what is "I" for, also?
Thanks.
