Not all beats have a "beat tag"..(plastic card attached to the roof). Tactical Teams (Civilian dressed officers, assigned to the Districts), drive in unmarked but known cars, Covert Units (Narcotics Unit, Vice Units-Prostitution, Gambling), utilize civilian cars, neither marked or known...just to name a few. The current Beat Unit Designators on these sites are quickly outdated as numbers change often. The latest is the 67xx Series Unit. This is the Gang Enforcement Unit recently formed. The 3rd Number designates the Area they're assigned...(6714H..Assigned to Area 1..6754H...Assigned to Area 5..etc. ) They usually wotk the Zone they're working in, but the PDT's are logged in on City-Wide 4 as the rest of the OCD (Organized Crime Division) is. The 42xx Series Units...Targeted Response Unit (Known as TRU). They operate on both City-Wide 1 and the Zone of the District they're in. 43xx and 44xx Series Unit...Mobile Strike Force (M.S.F.) Also assigned to City-Wide 1 and the Zone of the District they're in. As you can see, it can be quite a challenge to listen to the Chicago police, but that's what makes this hobby different.