# PSK

AI-generated

Phase-shift keying:
data sent as changes of phase of a single audio tone,
packing more bits into each symbol than [AFSK](../afsk/index.html.md) does.
The packet modems follow the ITU modem standards:
2400 bit/s QPSK as V.26 and 4800 bit/s 8PSK as V.27.
V.26 comes in alternatives A and B,
and both ends need to agree on which.

## References

* [ITU-T V.26](https://www.itu.int/rec/T-REC-V.26) and [V.27 ter](https://www.itu.int/rec/T-REC-V.27ter)
* [Phase-shift keying on Wikipedia](https://en.wikipedia.org/wiki/Phase-shift_keying)