The P-500 processor is available in three versions to meet the requirements of permanent system installers and portable system operators. Each includes servo-loop protection circuits, time and frequency domain correction and a precision front-end utilizing factory-matched components for high Common Mode Rejection. All models feature front panel function switches (which retain their settings through power-up/power-down cycles), turn-on/turn-off muting and Apogee\'s unique PAR™ adjustable protection circuitry. PAR (Positive Amplifier Return) senses the output of the amplifier and engages low distortion limiters to aid in protecting the drivers under abusive conditions. By selecting a \"User Preset\" mode, the protection circuits can be adjusted to match a wide range of power amps.