Revolutionary digital music-on-hold playback system supports MP3 and WMA audio formats. The unit has 16mb of on board memory preloaded with over 57 minutes of great sounding licensed music content, so it™s ready to go right out of the box. Add new content to the player by connecting to a PC via the USB port or just slip in a Secure Digital (SD) Card with new content. By adding a SD Card you can increase the memory to 1GB.