同义词
1)automatic exchange,automatic telephone switchboard,dial exchange,自动电话交换机2)automanual telephone switch board,半自动电话交换机3)step-by-step automatic telephone system,步进制自动电话交换机4)code switch automatic telephone system,码条式自动电话交换机5)panel system,升降制（自动电话交换机）6)private automatic branch exchange(PABX),专用自动电话交换机
