eKlasse EKBTEP15XM Bluetooth Sports Headset (Black) Power: Li-polymer 3.7V (80 mAh), Working voltage : 3.7V, Frequency Range: 20Hz-20KHz, Modulation / Channel access: GFSK,8DPSK,Π/4 DQPSK/79 Channels, Channel Spacing: 1MHz, Receiver Sensitivity: ≥80Db, Antenna type / Gain: PCB Antenna / -0.61dBi