The AG-51 Audio Generator contains a low distortion 20 Hz to 200 kHz sine wave generator, an SMPTE standard intermodulation signal generator and a fixed frequency sine wave generator at 3.15 kHz for wow and flutter tests. Signal outputs are simultaneously available at levels of up to +20 dBm (equivalent sine wave power for complex signals) at separate left (L OUT) and right (R OUT) output connectors. Outputs may be selected for left (L) only, right (R) only, left and right in phase (L+R), and left and right in phase opposition (L-R). Fully balanced or unbalanced outputs at impedance levels 150 ohms or 600 ohms are front panel selectable. Three precision attenuators (10, 1.0 and 0.1 dB) provide a dynamic range of 99.9 dB in 0.1 dB steps. Attenuator dials display the output level directly in dBm in the 150 ohm source impedance configuration. Automatic output leveling circuitry with a built-in self-test feature provides a constant output level thereby eliminating the need for output metering. In the TEST mode the generator output level is reduced to zero, a useful feature during noise measurements.