Note
Service magazine, Nov 1934, p. 442.
The model 500 is what Egert called a "Visual Resonance Indicator," using a cathode ray tube, and "all-wave" signal generator. This device provides direct reading resonance indications for all types of intermediate, broadcast and shortwave frequency alignment tests, and may also be used for visual indications of selectivity curves, adjacent channel selectivity, AVC action, RF signal distortion, presence of regeneration or oscillation in circuits, hum measurements, vibrator-transformer operation, AF harmonic distortion, noisy circuits, and so on.
The model 500 uses a type H72 cathode-ray tube, a 6F7 as frequency modulated oscillator and buffer amplifier, a 75 as diode rectifier and AF amplifier, a type 6A7 as all-wave oscillator and mixer tube. A type 84 tube serves as the rectifier supplying voltage for the modulated oscillator, audio amplifier and all-wave oscillator. A type 143D tube is used as a rectifier for the cathode ray tube voltages. Focusing adjustments are provided on the front panel. Due to the circuit employed, the attenuation is said to be equally accurate on all frequencies. The all-wave oscillator which is a part of the model 500 unit, covers a range of 100 kHz to 22,000 kHz. The oscillator dial on the front panel can obtain an accuracy to an absolute value of 1/10 of 1 per cent of the frequencies desired.