It is in reference to the staff body warn camera. No other audio recording is in use on Avanti, with few special exceptions such as recording a training video etc but that would be obvious where it is the case.
In regards to GDPR it is not a breach for a staff body camera to record credit card details due to the way the data is held securely, and a proviso that should the footage be required, for example in court, it can have the affected section removed if it will be played in open court, though this does have to be discussed with the judge I belive (my TOC hasn't needed to find out yet!) The recordings are not accessible except to a few staff who have specific additional training because of the sensitivity of some of the data involved (and the nature of what such footage sometimes shows).