A “high frequency” output gives the original, unaltered signal. Such an output is used to record the high frequency sound on a device capable of recording high frequencies (a computer with high-speed sound card or a high-speed recorder). The D200 detector has a high frequency output available all the time, while the other D2xx detectors don’t. However, pushing the Comment button will feed the original, high frequency signal from the microphone to one of the two output channels on the D230/240x detector. So, as long as you push this button, you have the high frequency signal available for recording.