两年前,笔者所在的工厂将原有老式拨盘电话机,全部更换为德赛HA1218(IV)P/T型按键电话机。经过一年多的使用,这些话机相继出现了各式各样的故障,其中尤以无振铃故障最多。通过对这些无振铃故障话机的修理。发现故障竟然出奇的一致,几十部电话机的故障点全部出在振铃电路C301与R301相连的焊点上。不是开 Two years ago, the author’s factory replaced the original old dial telephone, all replaced by Desai HA1218 (IV) P / T key telephone. After more than a year of use, these phones have appeared in a variety of failures, especially in the most ringing failure. Pass the repair of these ring-less phones. Found surprisingly unexpected failure, dozens of phone fault point all in ring circuit C301 and R301 connected to the solder joint. Not open