Palmer's Monicon L Passive Monitor Controller is an analog device that connects computers or audio interfaces, via stereo aux inputs (L/R RCA sockets, and a 3.5mm TRS jack for unbalanced inputs) or stereo inputs with combo XLR-1/4" balanced sockets, to two sets of self-powered monitors. The power supply is used for the LEDs, which indicate input and output selection, and for the headphone amplifier. The layout makes switching and level changes easy, with its push-button switches and large volume and headphone knobs.

You can A/B outputs one and two, or listen to both simultaneously using output selector switches. The mono XLR output is always active and enables you to connect an additional speaker or sum a stereo output. PFL mode facilitates stereo and main aux input monitoring regardless of onboard level settings.