What does the police radio code 10-21 signify?

• A. Disregard
• B. Standby
• C. Call by telephone
• D. Send backup

Answer: (C)

The main concept here is understanding how police radio codes convey the method of contact. 10-21 specifically means to contact someone by telephone. This instruction tells a unit to switch from radio communication to a phone call to relay details or coordinate off the air. It’s distinct from standby, disregard, or sending backup, which refer to different actions or statuses rather than how to reach someone by phone. Because the code 10-21 is about establishing a telephone contact, it best fits the option meaning “call by telephone.”