In APCO 10-codes, 10-40 refers to "Silent run, no lights or siren."
This code is used by law enforcement officers to indicate that they are responding to a call or situation but will do so without activating their emergency lights or siren. This typically means that the response does not require immediate urgency or that the officer is proceeding in a way that minimizes disruption to the public.
For example:
- Officer: "Dispatch, I'm on my way to the scene for follow-up, 10-40."
- Dispatcher: "Understood, Officer. Proceed without lights or siren."
Using 10-40 helps maintain a lower profile during responses where urgency is not a factor, such as routine checks or situations that do not pose an immediate threat.