Z Code (like Q Code and X Code) is a set of operating signals used in CW, TTY and RTTY radio communication.
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 (ZAL = alter wavelength, The old C&W Z codes are not widely used today. | |
| 2. | APCO also developed a system of Z codes.[1] | |
| 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.
| Code | Meaning | Source | |
|---|---|---|---|
| I am closing down (until ...) | C&W | ||
| ZAP ... | Work ... 1. Simplex; | 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; | C&W | ||
| ZUJ | Stand by. | NATO |
