Cancel—Disregard (Flag Semaphore)

A semaphore procedural signal instructing the receiver to disregard the preceding transmission or identified part of it.

It is used when material already sent should not be acted upon, rather than merely correcting a single mis-sent character. The sender should restart or continue only after the cancellation is understood under the procedure in use.

The exact response and repetition convention depends on the signalling system or organisation, so both stations should use an agreed code.