目前,我校电话总机使用的是HJ905纵横交换机,也是我省各高校普遍采用的一种机器。在实践中发现这种型号的交换机,在转接外线电话时有如下缺陷:话务员一旦拨完被叫用户号码,对用户振铃,就只能等到用户取机应答,振铃才能停止,如果被叫用 At present, our school telephone switchboard is used HJ905 vertical and horizontal switches, but also a province of colleges and universities commonly used a machine. In practice, this type of switch is found to have the following drawbacks when transferring an outside line telephone: once the operator dials the called subscriber number and rings the subscriber, the subscriber can only wait for the subscriber to answer the call before the ringing can be stopped. If the call is answered Called