ACP 131 facts for kids

ACP-131 is a special rulebook that lists and explains Q codes and Z codes. These codes help people communicate quickly and clearly using radio. It is created by a group of countries called the Combined Communications Electronics Board (CCEB). These countries are Australia, New Zealand, Canada, the United Kingdom, and the United States. The rulebook is updated from time to time. When the meanings of these codes are translated into different languages, they help ships from different nations talk to each other. This is very useful during events like a NATO exercise, especially when everyone doesn't speak the same language.

How It Started

The first version of ACP-131 came out a long time ago. The U.S. military published it when radio telegraphy was new. It was made for radio operators who used Morse Code to send messages. This was done with a type of radio signal called continuous wave (CW).

This rulebook became super important for radio operators on both military and civilian ships at sea. It was used a lot before newer radio systems, like single-sideband telephony, were developed in the 1960s.

Why We Need These Codes

In the past, radio communication was tricky. Before we had landlines and satellites, radio signals could often fade out. This happened because of many things, like weather, how strong the radio transmitter was, and even the time of day. Sometimes, you could only send messages for a few minutes or hours each day.

Because of these problems, it was very important to keep radio messages as short as possible. This was especially true for Morse Code radio channels where many operators shared the same line. Everyone had to wait their turn to send a message.

Imagine a radio operator wanted to ask another operator, "How are you receiving me?" In Morse Code, that's a long message to tap out:

  ▄ ▄ ▄ ▄   ▄▄▄ ▄▄▄ ▄▄▄   ▄ ▄▄▄ ▄▄▄       ▄ ▄▄▄   ▄ ▄▄▄ ▄   ▄       ▄▄▄ ▄ ▄▄▄ ▄▄▄   ▄▄▄ ▄▄▄ ▄▄▄   ▄ ▄ ▄▄▄       ▄ ▄▄▄ ▄   ▄   ▄▄▄ ▄ ▄▄▄ ▄   ▄   ▄ ▄   ▄ ▄ ▄ ▄▄▄   ▄ ▄   ▄▄▄ ▄   ▄▄▄ ▄▄▄ ▄       ▄▄▄ ▄▄▄   ▄       ▄ ▄ ▄▄▄ ▄▄▄ ▄ ▄ 

But using the ACP-131 codes, the same question could be sent simply as "INT QRK". This is much shorter:

  ▄ ▄ ▄▄▄ ▄ ▄▄▄       ▄▄▄ ▄▄▄ ▄ ▄▄▄   ▄ ▄▄▄ ▄   ▄▄▄ ▄ ▄▄▄ 

This made radio communication much faster and more efficient.

If the person receiving the message heard it "loud and clear," they would reply "QRK 5":

  ▄▄▄ ▄▄▄ ▄ ▄▄▄   ▄ ▄▄▄ ▄   ▄▄▄ ▄ ▄▄▄       ▄ ▄ ▄ ▄ ▄ 

All these short codes saved a lot of time and effort for the radio operators.

If the receiving operator didn't understand, they would just send a question mark:

  ▄ ▄ ▄▄▄ ▄▄▄ ▄ ▄ 

Then the other operator would send "INT QRK" again:

  ▄ ▄ ▄▄▄ ▄ ▄▄▄       ▄▄▄ ▄▄▄ ▄ ▄▄▄   ▄ ▄▄▄ ▄   ▄▄▄ ▄ ▄▄▄ 

This is much easier than repeating the long phrase "How are you receiving me?"

If the receiving operator understood the message, they would send "ROGER" or just "R":

  ▄ ▄▄▄ ▄ 

The "R" and "?" codes look a bit similar, but they are easy to tell apart when you hear them.

Who Uses These Codes

According to another rulebook, ACP-125(F), these codes are used in radio talks involving Allied military groups:

• Q codes can be used by both civilians and military. They can also be used when civilians and military talk to each other.
• Z codes are only for use between military stations.

How Codes Are Used by Different Types of Communication

These codes are used in different ways depending on the type of radio signal or communication method:

• For civilian radio using continuous wave (CW): Q codes are used.
• For military radio using CW: Both Q codes and Z codes are used.
• For civilian ships using signal lamps: Q codes are used.
• For military ships using signal lamps: Both Q codes and Z codes are used.
• For military Flag semaphore (sending messages with flags): Both Q codes and Z codes are used.
• For military teletype machines: Z codes are used in the message's starting information.

Using Codes in Voice Calls

Some people say that Q codes and Z codes were not meant for voice calls. In voice calls, speaking in plain language is usually fast and clear. However, in military communication, these codes are still sometimes used. This is because radio conditions can still be bad, especially on certain frequencies. For example, if a voice message like "received one flash message" gets distorted, a Z code might still be understood because it sounds very distinct.

Here's an example of a simple military voice call:

• "Q. Lima Five this is Charlie Two – Radio Check Over."
• "A. Lima Five - roger, over."
• "A. Charlie Two - roger, out."

Even though these codes are mostly for non-voice communication, some amateur radio operators still like to use a few Q codes, like QSL or QRK, out of tradition or convenience.

See Also

• Q code
• Z code
• Morse code
• Continuous wave
• Radio
• 500 kHz