DOI:10.1049/ree.1984.0104

出版商:IERE    

年代:1984

数据来源: IET

摘要:

Large-scale integration parts are easily damaged by the transient currents that result from e.h.t. flashover in a cathode-ray tube. It is therefore necessary during design to provide adequate circuit protection and, further, to ensure by testing that the protection is sufficient to remove the likelihood that flashover-induced failures will happen during normal operation.The purpose of this work was to evolve a test method that could achieve universal acceptance, so that it could be applied to both monochrome and colour units containing hard- or soft-flash c.r.t.s.The method chosen usesQ-switched laser pulses to initiate flashover discharges to the focus electrode and then employs the focus-to-final-anode gap as a surrogate spark gap to transfer flashover energy to the remaining c.r.t. connections. The measurements taken during manufacturing plant life-testing have been used to confirm the number of discharges required in a test to verify design.

DOI:10.1049/ree.1984.0105

出版商:IERE    

年代:1984

数据来源: IET

摘要:

This paper describes a joint BBC/BT pilot scheme involving the transmission of broadcast quality sound and vision signals and other services over a 140 Mbit/s digital bearer between London and Birmingham. Terminal equipment, designed and constructed by the BBC, is described which assembles one PAL television signal, including teletext and associated stereo signal, with 12–5 Mbit/s available for further high quality audio channels, telephony, data and error correction. The means of transmission involves the use of an optical fibre system, a radio relay channel and a coaxial line system. Initial evaluative studies are briefly outlined.

DOI:10.1049/ree.1984.0106

出版商:IERE    

年代:1984

数据来源: IET

摘要:

Stepping motors, as digital machines, are commonly used in electromechanical systems since they can easily be interfaced to and controlled by computers. Electrical and mechanical interaction in multiple-motor systems, however, can lead to severe control problems, and in intelligent systems such as programmable XYtables, rotor position feedback from each machine is necessary to implement effective control algorithms.This paper describes new methods of detecting rotor position in stepping motors with chopper drives. By monitoring the motor phase current waveforms and detecting the chopping current rise-times, motor phase excitation angle may be varied continuously over a step cycle, and performance may be maximized.Two industrial applications are described: accurate trajectory control in an XY table, where close position coordination between two motors is necessary; and velocity control in a two-motor system where mechanical interaction creates a variable inertia load for one motor.

DOI:10.1049/ree.1984.0107

出版商:IERE    

年代:1984

数据来源: IET

摘要:

Commercially available speech synthesizers are now being used extensively in talking machines. As their numbers continue to grow, it is essential to establish standard evaluation tests as quality control checks in their manufacture. A contribution towards this goal is described in this paper. Listeners heard the output of two commercial synthesizers. By identifying the basic units of speech (phonemes) which are wrongly perceived and comparing these with known confusions arising in listening to real speech under difficult conditions, it was possible to identify the limitations of a given synthesizer.

DOI:10.1049/ree.1984.0108

出版商:IERE    

年代:1984

数据来源: IET

摘要:

In spite of their inherent mechanical advantages, the use of two-phase a.c. induction motors in control applications has faded during the last ten years in favour of d.c. motors. This is due mainly to their lower efficiency and difficulty in control, particularly when using d.c. supplies.This paper describes a new approach to the control problem based on the use of ‘six-step’ d.c.-a.c. inverter drives in which complementary pairs of power v.m.o.s. f.e.t.s are used to implement the inverters interfaced via timer chips to the controlling microcomputer.

DOI:10.1049/ree.1984.0109

出版商:IERE    

年代:1984

数据来源: IET

摘要:

The general properties of hybrid networks are described and two main types, the quadrature and the 0–180° types, are identified. A list of uses of hybrid networks in radio frequency circuits follows. Seventeen configurations of hybrid networks are given with diagrams showing the variations of their input and output parameters with frequency. The 3 dB transmission line coupler is described in more detail and multiplexers are mentioned.

DOI:10.1049/ree.1984.0110

出版商:IERE    

年代:1984

数据来源: IET