If you’ve ever watched an episode of television or a film with someone communication over the radio with a string of numbers, you may have wondered what deal is with phrases similar to “10-4.” While 10-4 is arguably the most well-known of their lot, these code phrases are known as “ten-codes” or “ten-signals;” despite the name, there are for more than ten of them. The ten element of each code, beginning each phrase with the word “ten” arose as a workaround for receiving parties with inaccurate communication devices.

The codes were initially conceived by Charles Hopper in 1937. Hopper had been serving the Illinois State Police as a comms director and grew frustrated with how the analog equipment would tend to lose the first few moments of a correspondence. Hopper eventually figured that if an officer were to begin a message with the word “ten,” that messages could be received by the other party without losing any of the pertinent information as the equipment warmed up to operational standards. The codified nature of these signals also had the beneficial side effect of expediting communications.

10-1 Receiving Poorty
10-2 Receiving Well
10-3 Stop Transmitting
10-4 Acknowlegemet Rec’d
10-5 Relay To
10-6 Busy
10-7 Out Of Service-At
10-8 In Service
10-9 Repeat-Conditions Bad
10-10 Out Of Service
10-11 Dispatching Rapidly
10-12 Visitors Present
10-13 Weather/Road Cond.
10-14 Convoy Or Escort
10-15 Prisoner In Custody
10-16 Pick Up Prisoner At
10-17 Conduct Investigation
10-18 Complete ASGD Quick
10-19 Return To Station
10-20 Your Location
10-21 Call Station (Phone)
10-22 Disregard
10-23 Standby
10-24 Trouble-Sand Help
10-25 In Contact With
10-26 Message Received
10-27 Complete Record Ok
10-28 Check Registration
10-29 Stolen And/Or Wanted
10-30 Against Rules/Reg.
10-31 In Pursuit
10-32 Is Do Opr Available
10-33 Emergency Traffic
10-34 Jail Break/Trbl. Station
10-35 Confidential Info.
10-36 Correct Time
10-37 Operator On Duty
10-38 Block Road (S) At Station By Phone
10-39 Message Delivered
10-40 Out For Meal
10-41 In Possession Of
10-42 Out Of Service-Home
10-43 Any Traffic For
10-44 Pick Up Papers At
10-45 Call_By Phone
10-46 Urgent
10-47 Blood Run
10-48 End/Did You Receive
10-49 Serving War. Capals
10-50 Stop Veh. (Tag 10-20)
10-51 Enroute
10-52 Est. Time Of Arrival
10-53 Coming By Office
10-54 Negative
10-55 Car Calling To Car
10-56 Meet…At…
10-57 At Pistol Range
10-58 At Road Patrol Office
10-59 Send Teletype/Comp. Mag.
10-60 Assist To Motorist
10-61 Need R.P.SGI On Scene
10-62 Need R.P.LT On Scene
10-63 Need Bomb Squad (Scene)
10-64 Need Crime Lab (Scene)
10-65 Can You Copy
10-66 Cancel
10-67 Serving Civil Process
10-68 Legal Advice/Advisor
10-69 Send Narc.Agent
10-70 Send Wrecker
10-71 Send Ambulance
10-72 Send Helicopter
10-73 Open Gate S.O
10-74 Re-Call
10-88 Where Can Be Reached
10-89 On Page Service
10-90 Scramble (Code ABCD)
10-91 Detective And Vice Freq.
10-92 Police Comm. Freq
10-93 Detective Needed
10-94 Send Back-Up Car
10-95 Computer Check
10-96 Radio-Telephone Patch
10-97 Arrived At Scene
10-98 Complete Assignment
10-99 Unable Receive Signal
10-100 Alert-Remain Contact With
10-101 Log On Digital
10-102 Log Off Digital
10-103 Ack. Digital Mag. Screen
10-104 Computer System Down
10-105 Send Jail Wagon
10-106 Medical Asst Needed