The Krohn-Hite Model 4500 is an ultra-low distortion, stable amplitude oscillator designed for test and measurement applications in the 1Hz to 100kHz frequency range. The 4500 produces a virtually "distortion free" (<0.001%) sinewave for measuring harmonic distortion in audio pre-amplifier and power amplifier circuits. It also generates squarewaves with aberrations of less than 5% peak to peak amplitude. The exceptionally flat response of the 4500 (+0.05dB) eliminates the need to constantly monitor voltage levels during amplifier response tests. The unit delivers up to 7 volts rms open circuit to MAIN and INVERTED OUTPUTS of 600 ohm impedance. A MAIN OUTPUT of 50 ohms impedance is also provided. A four position pushbutton ATTENUATOR calibrated in 20dB steps together with a 30dB vernier provides a total dynamic range of 90dB. Amplitude and frequency stability varies less than 0.001% with a 10% change in line voltage. Sumultaneous INVERTED (180°) OUTPUT is provided for synchronizing a scope or as an auxiliary output. The output is fixed at 7 volts rms from a 600 ohm source impedance. Frequency tuning is provided by a 10:1 tuning dial and a 5 band decade multiplier . When combined with Krohn-Hite' s Ultra-Low Distortion Analyzer 6800A/6900 Series, it provides a complete distortion measurement system.