Phoenix pd

[SCPD]

When I was in LA I listened to the LAPD and when a new call went out the dispatcher would advise whether it was a code 2 or code 3 call. Why dont the dispatchers in Phoenix say that and how do the officers know whether to go code 2 or 3. A lot of times when there is a physical fight hot call you can hear the sirens in the backround when th officer is talking and other officers dont have there sirens on? Why? I was just curious.

Thanks