The AKG CU 4000 is a dual charging unit for the AKG BP 4000 rechargeable battery pack. The unit gently charges the battery packs in approximately 1 hour (typical). Charge Balance Management replaces the power drawn from the battery only. Several monitoring circuits and a temperature sensor prevent the battery pack from being overcharged. The dual bays are designed to accommodate BP 4000 battery packs or actual HT 4000 and PT 4000 transmitters for "drop-in" style charging.