VTech LS916 Retro Handset One-touch answer button Press to answer or end calls. Handset volume control Slide to adjust the listening volume. Audio switch: Further increases compatibility with different brands of Smartphones. 3.5mm audio plug: Compatible with wide range of Smartphones in the market.9 feet coiled cord increases flexibility. Retro style, Reduces cell phone radiation, Excellent sound quality, Works with most Smartphones