"Mike" wrote in message
...
what is it and why do i need this?

If what you are trying to listen to is "trunked" you can hear it with many
scanners that are not trunk tracking, but you often will only hear parts of
a conversation. You do not need it if there is no trunked systems in range.
If you tell where you are, others could probably tell you if there is any
reason for one where you are.
--
Gun Control:
Making the world safe for Thieves, Rapists, and Murderers, since 1968.