Hello. Yes, right. It is also necessary because of a power failure. Here from the FAQ on the support page: If there are batteries in the baby unit, it also switches automatically to battery operation in the event of a power failure. https://www.philips.ch/c-p/SCD560_00/avent-audio-monitors-dect-babyphone/support

the parent unit is rechargeable and can be reached wirelessly for up to 18 hours until the next recharge