Further improvements in a new type of simple detector are described and its operation shown to be the result of ionization of sodium vapor, consequent dissipation of the space charge and the increased current to the "collector" electrode secured thereby. A condition of equilibrium is obtained and is broken up by an impressed signal. On account of the inherent and controllable time element a gradual decrease in anode current for a series of input impulses is secured, resulting in a large alteration of current for impulses of low amplitude and consequently a strong response for weak signals. Power characteristics are given and possibilities indicated of the use of this device in various types of receiving circuit and also in measurement of signal strength, such as for the observations of fading