**Hertz**- Heinrich Hertz, well known experimenter that was the first to experimentally show the existence of electromagnetic waves in 1887. This breakthrough proved James Clerk Maxwells theories rigth.
- Hertz, a scale for frequency named in honour of Heinrich Hertz.
The frequency in Hertz is equal to the number of cylces of a
repetitive waveform that occur within one second. Cycles are
dimensionless and therefore is frequency derived from time only.
1 Hz = 1 cycle/s = 1/s

**Highpass**- Highpass is the name for a class of filters. A typhical highpass filter will be a approximation to the highpass brickwall filter. Highpass filters will suppress lower frequencies while letting higher frequencies pass. The brick wall model will completely suppress the lower frequencies while leaving the high frequencies untouched, all this with a sharp edge at the cutoff frequency. Ideal filters isn't part of reality and the approximations are many. Similar brickwall models exist, like lowpass, bandpass, bandstopp and allpass.
**HP**- Short for highpass.
**Hz**- SI standard short for Hertz annotating frequency.

(C) 1997, 1998, 1999 Magnus Danielson <cfmd at bredband dot net>