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,<br/>ZAP = ack please,<br/>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"
|+
|-
! Code
! Meaning
! Source
|-
|
| I am closing down (until ...)
| 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 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;<br/>2. IFF sets for 10 minutes in area denoted except for ships with the following
| C&W
|-
| ZUJ
| Stand by.
| NATO
|}
See also
- ACP-131