Many systems have an inaudible tone generated to "open" the frequency. Many agencies share the same frequency and this privacy system keeps you from having to listen to traffic, possibly from other states.
When this is part of your system there is up to a one second delay before you can actually transmit voice over the frequency. This applies to both car radios and consoles.
Hope this helps you understand why you need to pause after you key the mic before starting to speak.
- Bob Hanson
C. S. I.
Can't Stand Idiots