Item Type: Wireless Earbud Monitor System Material: Iron Shell Frequency Range: 518-554MHz Headphone Output Interface: 3.5mm Stereo Jack Transmitter Power Supply: DC12V/300mA Receiver Working Time: More than 12 Hours Receiver Battery: 2xAA Batteries (Not Included) Operating Range: Approx. 100m/109.4yd (Open Environment without Obstruction) RF Transmit Power: <10nW Dynamic Range: 90dB Harmonic Distortion: <1% (1KHz, 20KHz Frequency Deviation) Frequency Response: 40Hz-18KHz Headphone Output Power: 65m (32 OHM) Voltage: 110-240V Package List 1 x S3 Transmitter 1 x S3 Receiver 1 x Power Adapter 1 x Manual 1 x Antenna 2 Pairs x Ear Caps 1 x Headset 1It's reliable RF connection coverage up to 100m,and it has a signaltonoise ratio of up to 90 dB provides clear and complete audio. 2No complicated menus, but simple volume and mixing control buttons, and transmitter and receiver are all metal shell, sturdy and durable. 3There is no limit to the number of S3 receivers that can be used at the same frequency. 4Small and portable, the wireless earbud monitor system has three different receiving modes for you to choice. 5Each frequency band can use up to 8 sets of wireless monitoring systems at the same time.