| 摘要 |
PCT No. PCT/AU87/00097 Sec. 371 Date Oct. 19, 1988 Sec. 102(e) Date Oct. 19, 1988 PCT Filed Apr. 13, 1987 PCT Pub. No. WO87/06787 PCT Pub. Date Nov. 5, 1987.A protection device is provided for a telephone having a two wire subscriber line and an earth line. The protection device comprises a single surge protection device connected between a bridge rectifier polarity guard and the remainder of the telephone circuitry, which is connected to the output of the polarity guard. Three diodes are used to interconnect the earth line and the pair of output lines from the polarity guard to the surge protection device in such a way as to prevent surges from being fed to the remainder of the telephone circuitry. The surge paths including one or two arms of the polarity guard.
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