Equestrian Australia: Code of Conduct for Jumping Warm up arenas.

Further information:

207.3 Use of electronic devices – including in the Warm-Up arena:


207.3.1 Mobile phone devices, other electronic communication devices, and earphones may never be used by an Athlete while mounted in the Warm-Up Arena during a Competition. Failure to comply with this Article will incur a Warning in accordance with JRs Art 261.


207.3.2 Mobile phone devices, other electronic communication devices, and earphones may never be used by an Athlete in the Competition Arena during a Competition. Failure to comply with this Article will result in Elimination in accordance with JRs Art 263.4.


207.3.3 Athletes, grooms, or any other person may wear one earphone at any other time while mounted.

https://www.equestrian.org.au/jumping-rules