Serounder Bluetooth Headset, Sport Bluetooth 4.1 Neckband Earphone Stereo Headphones Headset w/Mic, TF Card Slot and Hands- Calls(Green) Bluetooth 4.1 Technology: Latest Bluetooth 4.1 technology features much lower power consumption, more stable , clearer stereo sound production. And the Bluetooth working distance is up to 10M. Works with most smartphone, tablets and ot Bluetooth Headsets are compatibles with almost every Bluetooth enabled devices such as Cell Phone/Laptop/PC/Tablet. Support up 32G TF card: Just insert a TF card loaded with your favorite songs, no need of mobile phones or other auxiliary devices, you can directly enjoy music. Pair to your Cellphone: 1. Need to be Off status or turn off the headset. 2. Press the "Play/ Pause" for about 3 seconds until the blue lights start flashing quickly. 3. Turn on the Bluetooth function of your cellphone and search for the bluetooth headset and select "SPORT-BT". 4. Enter the code "0000" if necessary. 5. If paring is successful, "Connected" will show on the cellphone. Power OFF the Headset: 1. Power Off: Press the "Play/ Pause" for about 4 seconds until the blue light indicator goes off. Answering a Call: Press the " Play/ Pause" of the headset. Rejecting a Call: Press the "Play/ Pause" for 2 seconds, then release. Redialing the last called number: Double press the "Play/ Pause". Specifications: Bluetooth version: Bluetooth 4.1 + EDR, two transmitter standard Frequency coverage: 2.402 ~ 2.480GHz ISM band Channel: 1MHz 79 channel, B / W Sensitivity: -80dbm Bluetooth range: Up to 10m / 30FT speed: 57 ~ 723Kbps Stereo compression ratio: 44.1 / 48kHz NFC: Support : Point to point Single or binaural: Bilateral stereo Charging power: PC USB, 5V Charging power: Input 110 / 220V 50/60 Hz Battery: 150mA Charging time: 1-2 hours Standby time: 30 days