The Coleman Audio CA500M is a 4 band stereo equalizer. The inputs & outputs are balanced on XLR connectors.
 
The EQ in switch turns the entire equalizer on or off. The high frequencies (8kHz, 10kHz, 12kHz and 16kHz) can be switched between shelving or peak EQ with 5db of boost or cut in 1db discrete steps.
 
The low frequencies (30Hz, 60Hz, 100Hz, and 150Hz) are shelving EQ with 5db of boost or cut in 1db discrete steps. The two mid bands are peak equalizers with frequencies overlapping by 1/4 octave and have up to 3.5db of boost or cut in 1/2db discrete steps.
 
The stereo/mono switch allows the Coleman CA500M to become a mono EQ unit. The audio passes through the left channel first and then through the right channel providing more EQ options. The circuits are designed to musical scales, not to mathematical relationships and the variable “Q” circuits maintain the tonal balance as the amplitude is adjusted.