Audio 2000s AWM6113 Dual Channel Rechargeable VHF Wireless Microphone System Balanced and Unbalanced Audio Outputs. Band: VHF Fixed Frequencies (170-216MHz) . Frequency Display . 100V-120V AC Power Supply. Rechargeable Mechanism built-in right on the top of receiver for convenient use Prior to use the system, both of the handheld transmitters need to be charged fully for at least 4 hours. Please use rechargeable batteries when charging the handheld transmitters. When charging the handheld transmitters, please make sure the receiver is at OFF position while power supply still plug to the wall. This way will charge both microphones at the same time. Charging with receiver ON will only charge one transmitter at the time. Both antenna need to be position at 45 degrees angle. Make sure that the antenna is not too close to the wall or TV. If there is a static noise appear when turn on the transmitter, unplug the AC adaptor or power supply and revise then plug in again.