DIY source selector kit for LUCIA installation amplifiers. Four-position rotary switch with resistor ladder, white knob, Euroblock receptacle, and cable connector — wires into the GPI port on any LUCIA model. Configurable for single-channel or ganged source selection, enabling custom wall plates that switch between background music, paging, and auxiliary inputs. EU and US wall-enclosure variants drop into standard single-gang back boxes for a finished, integrator-built control surface.