903 is a passing call.. Stopping in to say hello, or just having an of and on presence in an area. The public
can call their local station and ask for passing calls if there is an ongoing problem in an area, eg, drug dealing, drinking on a corner, vehicle break-ins, etc.
908 is for riding Muni, 908 was added a couple of years ago to make tracking Muni calls easier. Used to be all included in 903.