ITU-T Q 30-1988 IMPROVING THE RELIABILITY OF CONTACTS IN SPEECH CIRCUITS《改善话音电路中接点的可靠性》.pdf

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1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU%.%2!,G0G02%#/-%.$!4)/.3G0G0/.G0G04%,%0(/.%37)4#().G0G0!.$G0G03).!,).).4%2.!4)/.!,G0G0!54/-!4)#G0G0!.$3%-)G13!54/-!4)#G0G07/2+).)-02/6).G0G04(%G0G02%,)!“),)49G0G0/b) use of high contact pressure;c) double con

2、tacts;d) lubrication (with suitable oils) of certain non-precious metal contacts in the case of sliding contacts;e) direct current “wetting“ of contacts, care being taken to avoid the introduction of noise due to transientswhen the contacts are made or broken;f) air filtration or other protective me

3、asures to avoid dust;g) the maintenance of suitable humidity;h) the use of protective covers;i) protection against fumes, vapours and gases;j) avoidance of the use, near contacts, of materials likely to be detrimentral to the contacts.When voice-frequency signals are sent over a transmission path, as it is not possible to use direct currentwetting for the voice-frequency signal transmitting contacts due to the surges which occur on closing and opening thecontact, it is preferable to use static modulators with rectifier elements.