Z code

Z Code (like Q Code and X Code) is a set of operating signals used in CW, TTY and RTTY radio communication.

Distinct versions
There are at least three sets of Z codes.

Many of the old C&W codes are derived from mnemonics The old C&W Z codes are not widely used today.
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 * 1.
 * One set of codes was originally developed by Cable & Wireless Ltd. (the Cable & Wireless Service Z code) for commercial communications in the early days of wire and radio communications.
 * (ZAL = alter wavelength, ZAP = ack please, ZSF = send faster, etc.)
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 * 2.
 * APCO also developed a system of Z codes.
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 * 3.
 * NATO forces independently developed a later set of Z codes for military use and inter-language needs. The NATO Z codes are still in use, and are published in the unclassified document ACP-131.
 * }

There are other sets of codes internally used by Russia's military and other operating agencies.

Examples

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! Code ! Meaning ! Source
 * + Some example Z codes
 * ZAL (...) ...
 * I am closing down (until ...) due to ...
 * C&W
 * ZAP ...
 * Work ...
 * 1. Simplex; 2. Duplex; 3. Diplex; 4. Multiplex; 5. Single sideband; 6. With automatic error correction system; 7. Without automatic error correction system. 8. With time and frequency diversity modem
 * Work ...
 * 1. Simplex; 2. Duplex; 3. Diplex; 4. Multiplex; 5. Single sideband; 6. With automatic error correction system; 7. Without automatic error correction system. 8. With time and frequency diversity modem


 * C&W
 * ZBK
 * Are you receiving my traffic clear?
 * NATO
 * ZBK 1
 * I am receiving your traffic clear
 * NATO
 * ZBK 2
 * I am receiving your traffic garbled
 * NATO
 * ZBM 2
 * Place a competent operator on this circuit
 * C&W
 * ZLD 2
 * I cannot transmit pictures
 * C&W
 * ZSF ... (...)
 * Switch off ... (except ...)
 * 1. IFF; 2. IFF sets for 10 minutes in area denoted except for ships with the following call signs ...
 * I cannot transmit pictures
 * C&W
 * ZSF ... (...)
 * Switch off ... (except ...)
 * 1. IFF; 2. IFF sets for 10 minutes in area denoted except for ships with the following call signs ...
 * 1. IFF; 2. IFF sets for 10 minutes in area denoted except for ships with the following call signs ...


 * C&W
 * ZBW ...
 * Change to backup frequency ...
 * C&W
 * ZBZ ...
 * Measure of printability
 * 1=Garbled / unreadable, up to 5=Perfect
 * Measure of printability
 * 1=Garbled / unreadable, up to 5=Perfect


 * C&W
 * ZUJ
 * Stand by.
 * NATO
 * }
 * }