故障现象分机拨打外线和通话正常,但作被叫时不振铃。分析检修依经验分析.分机取机拨号和通话正常,说明线路无开路、短路故障,不振铃是电话机振铃电路异常。检修时将电话机接在其他线路试验振铃正常。用万用表测线路供电电压为48V,且拨号、通话正常,究竟什么原因造成分机不振铃呢?在配线箱内将总机与该 Symptom Extensions dial the outside line and call normal, but when called is not ringing. Analysis and maintenance according to the empirical analysis. Extension machine access dial-up and call normal, indicating no open circuit, short circuit failure, no ring is the telephone ringing circuit is abnormal. Repair the phone connected to the other circuit test ringing normal. Use a multimeter to measure line supply voltage of 48V, and dial-up, call the normal, what causes the extension does not ring it in the wiring box switchboard with the