DOI:10.1049/pi-b-1.1956.0109

出版商:IEE    

年代:1956

数据来源: IET

DOI:10.1049/pi-b-1.1956.0110

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The evolution of long-distance line-communication systems and the problems associated therewith are outlined. Attention is drawn to the need for certain international standards which facilitate the interconnection of such systems, and the work of the C.C.I.F. in this direction is mentioned. The evolution of radio-relay systems forming parts of internal telecommunication networks is traced, and the salient characteristics of modern systems are summarized. Emphasis is put on the need for international agreement on the preferred characteristics of radio-relay systems to facilitate their interconnection among themselves and with line-communication systems, The work of the C.C.I.R. in this field is mentioned, and the view is expressed that preferred characteristics should be adopted in the near future even though they may need to be reviewed, and perhaps revised and extended, after a number of years have elapsed.

DOI:10.1049/pi-b-1.1956.0111

出版商:IEE    

年代:1956

数据来源: IET

DOI:10.1049/pi-b-1.1956.0112

出版商:IEE    

年代:1956

数据来源: IET

DOI:10.1049/pi-b-1.1956.0113

出版商:IEE    

年代:1956

数据来源: IET

DOI:10.1049/pi-b-1.1956.0114

出版商:IEE    

年代:1956

数据来源: IET

DOI:10.1049/pi-b-1.1956.0116

出版商:IEE    

年代:1956

数据来源: IET

摘要:

Accurate information such as may be required for weapon control may best be transmitted over long-distance telegraph or voice communication circuits by using some form of digital representation or pulse code modulation. The paper describes a method by which the position of a scale attached to a datum shaft may be “read” photo-electrically as a binary number in much the same way as the scale of a surveying instrument is read in degrees and minutes. Data-transducers have been constructed to represent the angular position of a shaft as a 14-digit binary number, that is to an accuracy of rather better than one minute of arc. Special precautions have been taken in the design of the scale to prevent gross errors due to movement of the scale while it is being read. Such errors as do occur are examined in detail, since in some data-transmission applications they may not be sufficiently serious to justify the more complex equipment required for their complete elimination.

DOI:10.1049/pi-b-1.1956.0117

出版商:IEE    

年代:1956

数据来源: IET

摘要:

Certain special features must be taken into account in the design of a servo system which is to operate satisfactorily with digital data. In particular, the data are quantized in amplitude, thereby introducing non-linear effects; they constitute a series of samples instead of a continuous function, and there may be significant delays due to low-speed transmission circuits or digital equipment or both. All of these contribute in various ways towards reducing the stability of the system.The method of synthesis takes full account of the sampling and delay features and enables a degree of prediction to be incorporated which ensures that the regenerated data do not lag on the original under steady-state conditions. Effects especially attributable to amplitude quantization are then studied qualitatively. Since stability diminishes and the sensitivity to noise and instrumental errors increases as the time of prediction is increased, it is essential that the delay involved in the transmission of each sample should be minimized. Furthermore, the sampling servo system is less efficient than a continuous one as a smoothing device, and as much smoothing as possible should be applied at the sending end before sampling.

DOI:10.1049/pi-b-1.1956.0118

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The paper is concerned with the derivation of dynamically accurate electrical analogues for heat exchangers with a view to their application in the solution of automatic-control problems relating to the latter. The analogues are based on idealized equations describing the behaviour of the thermal processes involved.Two heat exchangers, both distributed-parameter systems, are considered, and two analogues are derived for each. One type of analogue is composed almost entirely of passive components but the other contains electronic amplifiers and employs a feedback technique.The design and construction of a passive-network analogue is described, and its experimentally-determined frequency responses are given and compared with the theoretical responses of the heat exchanger. Finally, an example is given of the experimental application of the analogue in an automatic-control loop.

DOI:10.1049/pi-b-1.1956.0119

出版商:IEE    

年代:1956

数据来源: IET