16-line message format, or Basic Message Format, is the standard military radiogram format for the manner in which a paper message form is transcribed through voice, Morse code, or TTY transmission formats. The overall structure of the message has three parts: HEADING, TEXT, and ENDING. This heading is further divided into procedure, preamble, address, and prefix. Each format line contains pre-defined content. An actual message may have fewer than 16 actual lines, or far more than 16, because some lines are skipped in some delivery methods, and a long message may have a TEXT portion that is longer than 16 lines by itself. This radiotelegraph message format and transmission procedures have been documented in numerous military standards, going back to at least World War II-era U.S. Army manuals.
DD Form 1765, Incoming Service Message Log would be used to record received messages.
DD Form 1766, Outgoing Service Message Log would be used to record outgoing messages.
Current Definition and Usage
The 16-line format and procedures for transmitting it vary slightly depending on the communications medium, but all variations are designed to be harmonious and the procedures describe how to convert between the formats.
ACP-124
ACP-125 defines the format of messages relayed by voice
ACP-126 defines the format of messages relayed by radio teletype
ACP-127 defines the format of messages relayed by automated tape
When sent as an ACP-126 message over teletype, a 16-line format radiogram would appear similar to this:
RFHT DE RFG NR 114 R 151412Z MAR FM CG FIFTH CORPS TO CG THIRD INFDIV WD GRNC BT UNCLAS PLAINDRESS SINGLE ADDRESS MESSAGES WILL BE TRANSMITTED OVER TELETIPEWRITER CIRCUITS AS INDICATED IN THIS EXAMPLE BT C WA OVER TELETYPEWRITER NNNN
Some of the format lines in the above example have been omitted for efficiency. The translation of this abbreviate format follows:
Format Line
Message Text
Explanation
Line 2
RFHT
Station being called, which will receive the message
Line 3
DE RFG NR 114
Sent by radio station having the callsign RFG, station serial number 114
The concept of the standard message format originated in the wired telegraph services. Each telegraph company likely had its own format, but soon after radio telegraph services began, some elements of the message exchange format were codified in international conventions, and these were then often duplicated in domestic radio communications regulations and in military procedure documentation. Military organizations independently developed their own procedures, and in addition to differing from the international procedures, they sometimes differed between different branches of the military within the same country. For example, the publication "Communication Instructions, 1929", from the U.S. Navy Department, includes:
One procedure for messages transmitted "in naval form over nonnaval systems"
One procedure for exchanging messages with commercial radio stations
One procedure for messages transmitted within the Navy
One format for exchanging messages between the Army and Navy, called the "Joint Army and Navy Radiotelegraph Procedure", with the format shown on page 70.
