摘要:

It has often been demonstrated that when an electric current is passed across certain sliding contacts the friction undergoes a change. In most cases the flow of electricity across the junction is accompanied by an increase in the friction, but in a few instances a slipping action is produced. Both these effects have been applied, to the operation of telephone devices, etc., but only a tentative explanation has so far been given of many of the complicated phenomena with which they are associated. In this paper are described a number of experiments designed to elucidate these intricate processes, and in the light of these investigations an attempt has been made to build up a comprehensive theory of their action.

DOI:10.1049/jiee-1.1924.0014

出版商:IEE    

年代:1924

数据来源: IET

摘要:

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.

DOI:10.1049/jiee-1.1924.0018

出版商:IEE    

年代:1924

数据来源: IET

摘要:

Part I is devoted to an examination of the ordinary method of recorder working in wireless telegraph receivers, as affected by the damping of the receiver circuits. After a résumé of the significances of the decrement of any oscillatory system, its bearing on the possible speed of recording Morse signals is investigated. The quality (approach to correct Morse “shaping”) is estimated from calculated curves of amplitude of oscillation set up in the receiver by the incoming dots and dashes constituting the letter “1.” By comparing several such curves, a minimum practical value is found for the product of frequency and decrement and duration of Morse dot. The relation between speed of signalling and the requisite transmitter power is then investigated. Part I concludes (Section 5) with a summary and discussion of the results arrived at.In Part II an improved method of reception, called “receiver curbing,” is described and analysed. An estimate is made of the improvement obtainable, and practical circuits are given for putting the method into effect.

DOI:10.1049/jiee-1.1924.0020

出版商:IEE    

年代:1924

数据来源: IET

DOI:10.1049/jiee-1.1924.0021

出版商:IEE    

年代:1924

数据来源: IET