Head Unit
A term commonly used in the car hi-fi industry for a car radio in complex systems equipped with external power amplifiers.

High Input
High input in amplifiers, to which car radios without a preamp out can be connected to the signal of the integrated output stage with an adapter.

Highpass
Active frequency cross-over to control subwoofer/satellite systems, whereby the music signal is faded out below a selected frequency.

High-Power Output Stage
Car radio output stage with 20-25 watt RMS or 25-40 watts per channel max. power, created by special high-power transistors.