Manual of Wireless Telegraphy, Manhattan Electrical Supply Company, Number nine (1916), page 111:

DeForest  Audion  Detector

Type  RJ9
Type RJ9

      The essential principle of this instrument is that the control for the "B" battery is a potentiometer control, giving very close regulation of the "B" battery potential. The switch controlling the filament brilliancy automatically cuts the "B" battery off from the potentiometer when the filament is turned "off."

      This Audion Detector is provided with brackets so that it can be screwed to a table. If the operator desires to incorporate it in a receiving cabinet, this can be done readily without disturbing the wiring and parts.

      All the controls on this new panel type instrument are mounted on the front of the mahogany panel, which measures 5 by 13 inches.

      All metal parts are of lacquered brass.

      No batteries are furnished, but 50 volts are necessary for the "B" voltage and 6 volts for the "A" voltage to properly operate this instrument.

      Licensed for amateur or private use only.
List No.Price
8447  De Forest Audion Detector, R J 9    $28.00