Z code

---

title: "Z code" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["operating-signals", "encodings", "morse-code"] description: "Morse code operating signal of the US Army / NATO" topic_path: "general/operating-signals" source: "https://en.wikipedia.org/wiki/Z_code" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Morse code operating signal of the US Army / NATO ::

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. :{| |- style="vertical-align:top;" | 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. : Many of the old C&W codes are derived from mnemonics : (ZAL = alter wavelength, ZAP = ack please, ZSF = send faster, etc.) : The old C&W Z codes are not widely used today. |- style="vertical-align:top;" | 2. | APCO also developed a system of Z codes. |- style="vertical-align:top;" | 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

:{| class="wikitable"

+ Some example Z codes
! Code
! Meaning
! Source
-

| | I am closing down (until ...)

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 | 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 |- | ZBW ... | Change to backup frequency ... | C&W |- | ZBZ ... | Measure of printability : 1=Garbled / unreadable, up to 5=Perfect | C&W |- | ZLD 2 | I cannot transmit pictures | C&W |- | | Switch off ... (except ...) : 1. IFF;
9. IFF sets for 10 minutes in area denoted except for ships with the following | C&W |- | ZUJ | Stand by. | NATO |}

References

References

1. "Standard Z Signals".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::