For the virtual machine language introduced by Infocom, see Z-machine.
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.
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
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
Some example Z codes
Code
Meaning
Source
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
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 ...