Abstract :
The phenomenon of oscillation hysteresis exhibited by simple triode generators is discussed theoretically. A practical method of reception in which this phenomenon is utilized in a periodic manner is described. This method, which for convenience may be termed ¿periodic trigger reception,¿ is suitable for continuous-wave and spark signals. A low-frequency electromotive force is introduced in the grid circuit of a simple triode oscillator in such a way that high-frequency oscillations are not produced in the absence of an incoming signal. A small signal of high frequency is, however, sufficient to produce a train of free oscillations once every low-frequency cycle. Such free oscillations are rectified by the triode, and a signal of the impressed low frequency is heard in the receiver telephones. The system differs fundamentally from the Armstrong super-regenerative receiver in the following respects:¿ (a) The ordinary oscillation-hysteresis characteristic is followed in a ¿quasi-stationary¿ manner; (b) No self-oscillations are produced in the system in the absence of an incoming signal; and (c) The amplitude of the telephone signal is practically independent of the amplitude of the incoming signal and not proportional to it as in super-regenerative receivers. It has been discovered experimentally that oscillations may be maintained in a simple triode generator with extreme negative grid potentials such as would cut off the anode current entirely under normal conditions. A simple theory for the conditions necessary for such maintenance is given. An oscillator of this type is very efficient in that anode and grid currents are only permitted to flow for a very small part of the cycle.
