For generating AC voltage for clearing of the conveyors in case of fire or failure, a voltage of 400 V 50 Hz is required. That voltage is obtained from a battery set with the help of an inverter. That battery set is independent from the replacement power batteries of the hold-open device.
Maintenance-free batteries for alarm systems according to reference source VdS-2140 shall be used. The capacity of the batteries depends on the required efficiency.