2-channel limiter, with measuring microphone.
The SPL3 works just like the SPL2: the microcontroller continuously measures the input-level and attenuates the output level as much as necessary to keep the sound level below the given threshold.
But the SPL3 has another feature. A measuring microphone is connected so that it has the possibility to measure the audio-level from live-bands etc. This measuring microphone makes the SPL3 the ideal limiter for live performances where the band uses its own PA system. When, in live mode, the sound-level exceeds the threshold, the limiter can give a warning to the band (with a flashing light). If the sound-level remains too loud for a longer period of time the limiter will activate the sanction output and can, if desired, cut-off the mains supply of the band.