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The negative-resistance oscillator possesses many advantages over the ordinary triode feed-back types. The most common of negative-resistance oscillators, the dynatron, has not been generally adopted owing to its dependence on secondary emission, an unsteady property. The retarding-field negative-transconductance oscillator possesses the advantages of the dynatron without its disadvantages. This type of oscillator is discussed from the practical standpoint, the theoretical treatise having been given in a previous article. The oscillator will generate sinusoidal oscillations of any frequency from the lowest audio to 60 megacycles by simply changing the tuned circuit constants. It will function with direct plate and anode voltages of 2 and 4 volts, respectively, or 50 and 200 volts, respectively, or any intermediate values. An alternating-current output of a fraction of a volt to over 20 volts effective value is obtainable across the tuned circuit. The simplicity of construction and operation and the assurance of constant performance make this type of oscillator a valuable addition to the laboratory.