The CL-SES is a high-quality audio source switch that allows you to select from up to three input devices via automatic signal sensing or a manually operated switch. This gives you the freedom to install your choice of audio sources, without resorting to weak sounding FM modulators or cassette adaptors. The CL-SES can be used to expand the auxiliary input capabilities of the CleanSweep® CL441dsp or any head unit that provides an auxiliary line-level input, including many OEM head units.