i think i can answer this one, or at least shed a bit of light on it...
i have quite a few friends whom are officers, many of them i originally met wile driving an old subaru with a ghost in the wiring always had head lights burning out(they only lasted a couple days-two weeks at most) i got pulled over A LOT(working at a bar ina college town and leaving the bar with a headlight out will get you pulled pretty regurally, they're just looking for drunk drivers). anyway i became a familiar face to many of them, and always informed them that i had a liscence and wether or not i was carrying(they really appricite it btw, and they like folks who have CHP, shows you are a law abiding person willing to follow rules and work within the system, they like the courtousy of being told your carrying also) and working at the bar i've become friends with many of the guys just stopping through on random civility checks, responding to calls, or just enjoying themselves off-duty...
anyway, when they run your liscence(t-number as mentioned above) in this area atleast(ymmv), they will hear over the radio from the dispatch basically that subject is good to go, or get a code(iirc my buddy told me in h'burg dispatch will say "code 4") wich basically means standby for more info(info not meant to be heard by subject). they will turn or step away and say "unit___ go ahead" once you are out of earshot. the dispatcher will then tell them the information that triggered the code. things that could trigger the code responce includebut are not limited too: an outstanding warrant(being wanted for arrest), prior violence or assault history(espicially if toward an officer), prior gun charges, prior felonies(espicially if related to a violent or gun charge), blah, blah, blah, or if subject has a valid current CHP....
all these warning flags are meant to be an additional heads up to the officers for their personal safey(and in many of these cases rightfully so)...
usually it goes something like this...
cop: bluelights come on.
me: pullover someplace not so dangerous for ifficer, turn on flashers, roll-down window, hands in plain sight.
cop: liscence and registration please.
me: of course officer but first i feel it's my duty(though not legaly required in VA) to infor you that i am a holder of a CHP, and i am(or am not) carrying tonight/today.
cop: oh ok, no problem, thanks for letting me know...
i've been pulled over many times(again, it averaged no less than once a week and 2-3 times wasn't totally unheard of, but i found out now from an officer friend whom detained me several times, that i also looked like a guy they were looking for. and i had a mohawk a bunch of peircing and some tattoes, am often seen on way into or from a bar in a college town, i expected to be pulled over often, i fit the stereo type of a trouble maker and I DO thank officers for checking up on people who look the way i did), but after talking with the officers have rarelly ever gotten a ticket for much of anything since getting my CHP 8 years ago(2x for speeding on interstate, once for defective equipment)
now i have at times been preoccupied with trying to get somewhere, or "thinking damn-it, not again" and forgotten to tell the officers that i had a CHP and i've had officers unholster their weapons several times, and many more thumb open the latch on the holster, but never had a weapon pushed in my face(not assuming it happened either way just pointing out that their is a huge dfference between an officer unholster his weapon and approaching a vechical with it drawn, and having the officer "draw down" on you)
i can kinda sympathise theorethically with an officer being a bit cautious if he is informed a suspect(someones' wife or not) may be armed, yet in the initial face to face, the information was not volunteered. it'd probablly make me think "well why on earth didn't they tell me, as it's would have no big dead? so what are they hiding/up too?"