This 2.1 speaker system has a sleek knob control used for adjusting the volume level of the Prisma Bluetooth. The first is the master volume control. Control the volume using the dial and crank up the sound for your favourite songs, movies, and games. There is a halo light power indicator to let you know the system is ready to go. There is also a headphone output for private listening sessions. Finally, there is a 3.5mm auxiliary input, which can be used to play music from your smartphone.