[Ret10Echo]

Ohhh...the many, many problems with P25... Great idea, poor (nay...LOUSY) implementation. Interpretation by vendors and system configurations create interoperabilty nightmares. I spent some time explaining to a non-techie that just because it says P25 on the label does not mean it will operate with other devices sporting the P25 label. TIA-102 suite continues to march...vendors continue to apply as many "features" as possible to render devices incompatible (despite advertising). Something about company's whose names begin with "M"...dunno

To answer the question concerning "trunked" systems. A digital trunked network can still possess "talkaround" or peer-to-peer communications if configured to operate in such a manner. Of course that bumps up the spectrum support requirements...but there are always trade-offs. Purposeful application of interoperability channels or talk groups helps.

Operation and Maintenance costs (O&M)...yup, as soon as it is built it begins to break down. Nature of the beast. For organizations such as public safety that do not generate revenue for O&M, it quickly becomes problematic. Vendors will carry parts for your 15 year old system...but that's "Extra".

Encryption...difference between encryption in the public safety space and in military terms. Simple encryption is readily available, but managing that across a trunked system and when other users will be around becomes problematic. Key management is not easy when there are so many devices out there and the culture is one of open communcations.

Enough for now....