Z code
Z Code (like Q Code and X Code) is a set of operating signals used in CW, TTY and RTTY radio communication. There are two sets of Z-codes: one originally developed by Cable & Wireless Ltd. (the Cable & Wireless Service Z-Code) for commercial communications in the early days of wire and radio communications and another 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 sets of codes internally used by Russia's military and other operating agencies. The old C&W Z Codes are not widely used today.
| 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 |
| ZBK1 | I am receiving your traffic clear | NATO |
| ZBK2 | I am receiving your traffic garbled | NATO |
| ZBM2 | Place a competent operator on this circuit | C&W |
| ZLD2 | I cannot transmit pictures. | C&W |
| ZSF | Switch off...(1. IFF; 2. IFF sets for 10 minutes in area denoted except for ships whose call signs follow). | C&W |
| ZBW no. | Change to backup frequency no. | C&W |
| ZBZ(1-5). | Measure of Printability (Where 1=Garbled/unreadable & 5=Perfect) | C&W |
| ZUJ | Stand by. | NATO |
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.