NARROW-BANDING is required by the FCC; but P-25 digital and encryption are not. Many places are already using the new narrow band analog radios and you can't tell the difference most of the time, cuz it sounds just like any FM transceiver...
P25 and encyption are not part of narrowbanding...which is correct (obviously).
However, to quailify for most (if not all grants) these days for commuications, the radios themselves must be
capable of P25 operation. This does not mean that the radio
must come with the P25 option, but that you can upgrade it down the road.
Typically, the radio's are ordered with it anyways, because...why not?
Two-way encryption available to the general market (including your local cops) has been around since the 70's. The reason why you didn't see encyption often was due to cost, and the the voice quaility.
With the advent of digital voice, the encyption module now just encodes the digital data instead of doing the analog to digital conversion and encypting it. Because of this, your not losing any voice quaility than P25 in the clear. In addition, the cost of encyption itself has come down in price.
Your also looking at a smarter criminal. They buy scanners (always have) and with "great" features as Close call...if the cops are not using Nextel or cellphones, guess who they are going to hear should a survellence or other operations is nearby?
As I have experience in said field, the general public can be a help, or a hinderance in listening to scanners. For the most part, its a hinderance as 99% of the people listening actually have no clue what is going on. Although they may be hearing the back/forth, there are so many other forms of communications happening (MDT, cell, text pagers, etc) that people draw conclutions on less than full facts. This is when the scanner masterbators start to call police with "tips" that are not even realvant to calling friends or news stations with incomplete/incorrect information.
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Now, if your not using the proper scanner, or not with proper settings, there is a difference in listening to 25/30 voice and 12.5k voice.