where did the radio phrase 10-4 come from?

Answer 1

"Ten-Four" is a frequently used ten-code acknowledgment that a transmission has been received and understood. A "big ten-f our" means the received message is agreed with by the recipient. It is difficult to find where it actually originated, but it is part of standard CB jargon.

Ten-four "I understand, message received," is attested in popular jargon from 1962, from use in CB and police radio in the U.S. by 1950).

Using such terms for radio communication help with clarity and ensuring messages are well understood, so it probably originated for that purpose.

Here are the links I was able to find.

Answer 2

There are 200 10-Codes in current usage, approximately 50 of these are used by the police, fire and other types of radio operators, while others have combined meanings depending on the service. Below is a list of the most commonly used 10-Codes:
10-1 = Receiving poorly
10-2 = Receiving well
10-3 = Stop transmitting
10-4 = Message received
10-5 = Relay message to _____
10-6 = Busy, please stand by
10-7 = Out of service, leaving the air
10-8 = In service, subject to call
10-9 = Repeat message
10-10 = Transmission completed, standing by
10-11 = Talking too rapidly
10-12 = Visitors present
10-13 = Advise Weather/Road conditions
10-16 = Make pick up at _____
10-17 = Urgent business
10-18 = Anything for us?
10-19 = Nothing for you, return to base
10-20 = My location is _____
10-21 = Call by telephone
10-22 = Report in person to
10-23 = Stand by
10-24 = Completed last assignment
10-25 = Can you contact _____
10-26 = Disregard last information
10-27 = I am moving to channel _____
10-28 = Identify your station
10-29 = Time is up for contact
10-30 = Does not conform to FCC rules
10-32 = I will give you a radio check
10-33 = Emergency Traffic
10-34 = Trouble at this station
10-35 = Confidential information
10-36 = Correct time is
10-37 = Wrecker needed at
10-38 = Ambulance needed at
10-39 = Your message delivered
10-41 = Please turn to channel
10-42 = Traffic accident at
10-43 = Traffic tie up at
10-44 = I have a message for you
10-45 = All units within range please report
10-50 = Break channel
10-60 = What is next message number?
10-62 = Unable to copy, use phone
10-63 = Net directed to
10-64 = Net clear
10-65 = Awaiting your next message/assignment
10-67 = All units comply
10-70 = Fire at _____
10-71 = Proceed with transmission in sequence
10-77 = Negative contact
10-81 = Reserve hotel room for ______
10-82 = Reserve room for _____
10-84 = My telephone number is ______
10-85 = My address is _____
10-91 = Talk closer to the microphone
10-93 = Check my frequency on this channel
10-94 = Please give me a long count (1-10)
10-99 = Mission completed, all units secure
10-200 = Police needed at _____

Answer 3

10-4 is one of the common CB ten codes. Explanation follows:

What are Ten Codes?

Ten Codes are abbreviations of common questions and answers used on all types of radio. Profession CB'ers use Ten Codes to send their message quickly and easily. Additionally, Ten Codes can be readily understood by stations which may be receiving you poorly or when a language barrier is present. Learning Ten Codes is most often done by their use. Copy this list of some of the most common Ten Codes and keep them near your radio. Use these Ten Codes in your daily communications and soon you will have most of them committed to memory!

Common CB Radio Ten Codes

10-1 = Receiving poorly
10-2 = Receiving well
10-3 = Stop transmitting
10-4 = Message received
10-5 = Relay message to _____
10-6 = Busy, please stand by
10-7 = Out of service, leaving the air
10-8 = In service, subject to call
10-9 = Repeat message
10-10 = Transmission completed, standing by
10-11 = Talking too rapidly
10-12 = Visitors present
10-13 = Advise Weather/Road conditions
10-16 = Make pick up at _____
10-17 = Urgent business
10-18 = Anything for us?
10-19 = Nothing for you, return to base
10-20 = My location is _____
10-21 = Call by telephone
10-22 = Report in person to
10-23 = Stand by
10-24 = Completed last assignment
10-25 = Can you contact _____
10-26 = Disregard last information
10-27 = I am moving to channel _____
10-28 = Identify your station
10-29 = Time is up for contact
10-30 = Does not conform to FCC rules
10-32 = I will give you a radio check
10-33 = Emergency Traffic
10-34 = Trouble at this station
10-35 = Confidential information
10-36 = Correct time is
10-37 = Wrecker needed at
10-38 = Ambulance needed at
10-39 = Your message delivered
10-41 = Please turn to channel
10-42 = Traffic accident at
10-43 = Traffic tie up at
10-44 = I have a message for you
10-45 = All units within range please report
10-50 = Break channel
10-60 = What is next message number?
10-62 = Unable to copy, use phone
10-63 = Net directed to
10-64 = Net clear
10-65 = Awaiting your next message/assignment
10-67 = All units comply
10-70 = Fire at _____
10-71 = Proceed with transmission in sequence
10-77 = Negative contact
10-81 = Reserve hotel room for ______
10-82 = Reserve room for _____
10-84 = My telephone number is ______
10-85 = My address is _____
10-91 = Talk closer to the microphone
10-93 = Check my frequency on this channel
10-94 = Please give me a long count (1-10)
10-99 = Mission completed, all units secure
10-200 = Police needed at _____

Answer 4

It is part of the 10-codes, developed in 1937 and expanded in 1974 by the Association of Public Safety Communication Officials (APCO), allow for brevity and standardization of message traffic. They have historically been widely used by law enforcement officers in North America, although the trend is away from their use in recent years with more departments discouraging the use of ten-codes and encouraging "clear" or plain language communications.

10-4 generally means understood or OK or affirmative.

Answer 5

A bunch of "10 codes" also known as "ten signals" made popular in the 70's by APCO ( Association of Public Safety Communication Officials).