BS 50999:1992 Foreword 前言 This Britishi Standard has been prepared under the direction of the cable and Insulation Standards policy Committee and supersedes BS 5099:1974 which is withdrawn.. 本標準是英國關於電線電纜行業的標準，取代 BS 5099:1974 This edition of BS 5099 introduces a clause on calibration frequency, together with an associated annex on the procedure for checking the efficacy of the method of spark