摘要:

Electronic road toll collection has usually been carried out on the highway using an automatic vehicle identification (AVI) system. At the toll site, physical barriers are set up between lanes so that individual vehicles can be effectively detected. Problems arise, however, in the detection of vehicles on busy city roads where barriers between lanes are not desirable and the traffic does not always maintain lane discipline. A new AVI system using a randomised time division multiplexing (TDM) technique for detecting several vehicles simultaneously entering the detection zone is described in this paper. Laboratory experiments carried out for up to eight identification tags at the same time showed that all replies were detected for 900 interrogations. Collisions between replying signals did not occur. The high-speed transmission of serial data has, however, an error rate of 3–7%. Under laboratory conditions, the detection errors were eliminated simply by allowing the tags to reply twice.

DOI:10.1049/ecej:19910018

出版商:IEE    

年代:1991

数据来源: IET

摘要:

This is the first part of a two-part paper describing the use of digital techniques in professional sound recording. It outlines the processes of sampling, quantising and channel coding necessary for converting an analogue signal into a digital format suitable for recording on magnetic tape, as well as the signal reconstruction processes. Popular stationary and rotary head recording formats are described. The second part will cover the impact of digital technology on the post-recording production process.

DOI:10.1049/ecej:19910019

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The dimensions of semiconductor devices can now be reduced to the point where quantum-mechanical effects must be considered in device performance. New device concepts have therefore been proposed, and already realised, in which quantum-mechanical effects are used to achieve increased electron mobilities or in which interference phenomena are utilised. At present, the major drawbacks of nonoelectronics are the technological problems of realising the devices. The emphasis of this paper is on new technological concepts for device realisation. Additionally, an overview of proposed and realised devices is given. Future advances in nanofabrication may come from the development of the scanning tunnelling microscope and related systems.

DOI:10.1049/ecej:19910020

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The number of electronic mail installations world-wide is growing rapidly, especially in the United States. This paper discusses the need for an international standard for communicating electronic messages and describes the X.400 standard agreed by both the ISO and CCITT for an electronic messaging system. Work going on in the standards bodies to produce extensions to the standard are outlined.

DOI:10.1049/ecej:19910021

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A new wide-area data network is described. The network employs packet-switching techniques within a multiaccess, narrow-band cellular radio environment and provides a flexible alternative to copper wire telecommunications for short data message applications. Following a discussion of the network requirements, the paper describes the key design areas in terms of a layered model. A new data link layer protocol called dynamic slotted reservation Aloha is introduced. This protocol is optimised for the bidirectional communication of packets containing around 1000 bits of application data. The practical implementation is presented briefly before a number of the major applications are discussed.

DOI:10.1049/ecej:19910022

出版商:IEE    

年代:1991

数据来源: IET