The 10-codes have changed a bit over the years, but on paper they are all still 10-xx.
Historically the term "Signal" in NYPD meant "a report of". For example, A Signal 10-30 would meant "a report of a robbery in progress" as opposed to a confirmed 10-30. However, I think this tradition has been lost in antiquity and is no longer used this way. The term "signal" remains however and you will hear things like a signal 30, which is just an abbreviation for signal 10-30. You will also hear the phrase a confirmed signal 30 indicating that the tradition of signal meaning "a report of" is no longer valid.
So just like in plain English, slang becomes the standard, so too it appears with NYPD dispatch that "slang" is working its way into the "offical" dispatch terminology.
