View source for Z code

{{for|the virtual machine language introduced by Infocom|Z-machine}}
{{use dmy dates|date=November 2023}}
{{short description|Morse code operating signal of the US Army / NATO}}

'''Z&nbsp;Code''' (like [[Q Code]] and [[X Code]]) is a set of operating signals used in [[continuous wave|CW]], [[Teletypewriter|TTY]] and [[radioteletype|RTTY]] radio communication.

== Distinct versions ==
There are at least three sets of Z&nbsp;codes.
:{|
|- style="vertical-align:top;"
| 1.
| One set of codes was originally developed by [[Cable & Wireless Worldwide|Cable & Wireless]] Ltd. (the Cable & Wireless Service Z&nbsp;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 = '''a'''lter wave'''l'''ength,<br/>ZAP = '''a'''ck '''p'''lease,<br/>ZSF = '''s'''end '''f'''aster, etc.)
:
The old C&W Z&nbsp;codes are not widely used today.
|- style="vertical-align:top;"
| 2.
| APCO{{clarify|date=November 2023}} also developed a system of Z&nbsp;codes.<ref>{{cite web |title=Standard Z&nbsp;Signals |website=APCO International Historical Collection (apcohistory.org) |url=http://www.apcohistory.org/apco-collection/search/profile/article/A28953}}</ref>
|- style="vertical-align:top;"
| 3.
| [[NATO]] forces independently developed a later set of Z&nbsp;codes for military use and inter-language needs. The NATO Z&nbsp;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"
|+ {{big|'''Some example Z&nbsp;codes'''}}
|-
! Code
! Meaning
! Source
|-
| {{nobr| ZAL (...) ... }}
| I am closing down (until ...) {{nobr|due to ...}}
| C&W
|-
| ZAP ...
| Work ...
: 1. Simplex;<br/>2. Duplex; <br/>3. Diplex; <br/>4. Multiplex; <br/>5. Single sideband; <br/>6. With automatic error correction system; <br/>7. Without automatic error correction system. <br/>8. With time and frequency diversity modem
| C&W
|-
| ZBK
| Are you receiving my traffic clear?
| NATO
|-
| ZBK&nbsp;1
| I am receiving your traffic clear
| NATO
|-
| ZBK&nbsp;2
| I am receiving your traffic garbled
| NATO
|-
| ZBM&nbsp;2
| Place a competent operator on this circuit
| C&W
|-
| ZLD&nbsp;2
| I cannot transmit pictures 
| C&W
|-
| {{nobr|ZSF ... (...) }}
| Switch off&nbsp;... (except&nbsp;...)
: 1.&nbsp;IFF;<br/>2.&nbsp;IFF sets for 10&nbsp;minutes in area denoted except for ships with the following {{nobr|call signs ...}}
| C&W
|-
| ZBW&nbsp;...
| Change to backup frequency&nbsp;... 
| C&W
|-
| ZBZ&nbsp;... 
| Measure of printability
: 1=Garbled / unreadable, up to 5=Perfect 
| C&W
|-
| ZUJ
| Stand by.
| NATO
|}

==See also==
* [[ACP-131]]

==References==
<references />

== External links ==
* [http://www.kloth.net/radio/zcodes.php Ralf D. Kloth DL4TA – List of Z-codes] 
* [https://web.archive.org/web/20120906015123/http://jcs.dtic.mil/j6/cceb/acps/acp131/ACP131F.pdf ACP 131(F) – Communications Instructions Operating Signals]

{{Morse code}}

[[Category:Operating signals]]
[[Category:Encodings]]
[[Category:Morse code]]