All Call and Chime Adaptor - The BG-10C connects to LEF and LEF-C systems. The BG-10C provides a chime when a door station calls in (max three). It also provides functionality for the All Call button on the LEF-C and LEF-10S masters and an line-level input for music distribution. The BG-10C has tone, bass, all call voice and pre-tone volume, Chime volume and music volume controls.