The Model KAA4020 is a Class AB wideband RF power amplifier that delivers more than 500 Watts CW power into a 50-Ohm load over the frequency range of 1 MHz to 50 MHz. Power gain is a minimum of 57 dB. GPIB control requires the optional IEEE488.2/RS232 Interface Controller Module. The system features forward and reflected power indication on a front panel-mounted analog meter; Automatic Level Control (ALC); RF gain control; overdrive protection; full VSWR protection; input blanking, and over-temperature protection. On the basic model these features, plus remote power on/off control, are accessible for hard-wire remote operation through a 25-pin, D-subminiature connector. For a detailed description of these features refer to "SPECIAL FEATURES - KAA & KAW-SERIES SINGLE BAND RF POWER AMPLIFIERS". The Model KAA4020 is a 19-inch rack-mount unit, 8¾ inches high and 26½ inches deep. Construction is completely modular and all subassemblies can be readily removed. Forced-air cooling is by a highly reliable, tube-axial fan mounted on the rear panel. The amplifier operates from 187-265 VAC, 47-63 Hz line. The system may be placed in 'stand-by' mode with the BLANKING switch.