Z code

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For the virtual machine language introduced by Infocom, see the article under Z-machine.

Z Code (like Q Code and X Code) is a set of codes used in CW, TTY and RTTY radio communication. Actually, there are different sets of Z-codes: one originally developed by Cable & Wireless Ltd. for commercial communications in the early days of wire and radio communications, another one independently developed by NATO forces later for military needs and use. The NATO Z Code is still in use today, and is published in the unclassified document ACP-131. There are other set of codes internally used by USSR's military and other operating agencies. The old C&W Z Codes are not widely used today.

Some Example Z Codes

Code	Meaning
ZAL	Alter your wavelength
ZAP	Acknowledge, please
ZBK	Are you receiving my traffic clear?
ZBK1	I am receiving your traffic clear
ZBK2	I am receiving your traffic garbled
ZBM2	Place a competent operator on this circuit
ZSF	Send faster
ZBW #	Change to backup frequency #

In this example, the ZBK/1/2 is a Z code from the NATO military set, while the others are old C&W Z-codes. A lot of the old C&W codes are derived from mnemonics (ZAL = (a)lter wave(l)ength, ZAP = (a)ck (p)lease, ZSF = (s)end (f)aster, etc),

See also: Common Morse code abbreviations in the Morse code article