APTX & APTX LOW LATENCY SUPPORTED. Powered by premium CSR8670 chipset, TROND BT-DUO S not only supports the latest Bluetooth V4.1, but also adds aptX & aptX Low Latency to both the TX and RX modes. With aptX, you can enjoy CD-quality sound wirelessly over Bluetooth connections with aptX-source devices like TV's, phones or tablets; with aptX Low Latency, you can now watch video while listening to wireless audio in a synchronized fashion AND without any noticeable audio delay TX MODE: BLUETOOTH TRANSMITTER. By plugging TROND BT-DUO S to your non-Bluetooth audio sources (TV, iPod, Kindle e-Book reader or Nintendo Switch/3DS), you can enjoy high quality music wirelessly or listen to late night shows without disturbing your family members on your Bluetooth headphones or speaker. Please also order TROND TD-BH01 Over-Ear Bluetooth V4.2 Headphones (ASIN: B075VLWPXF) for the best low latency performance RX MODE: BLUETOOTH RECEIVER w/ VOLUME CONTROL. TROND BT-DUO S can upgrade your old wired headphones (such as Bose QC25/QC15) or speakers into wireless with the support for aptX Low Latency. Its volume/track buttons allow you to play/pause music, turn volume up/down, and select track forward/backward. (NO hands-free calling due to lack of microphone; cannot be powered up automatically while you start the car ignition)