400电话又称"全国统一接入码业务"，由10位数字组成，是电信运营商专为企事业单位设计的全国统一的、强大的虚拟电话总机，所有拨打这个400电话总机的来电均被转接至预先绑定的实体电话上接听，可以实现企业对外宣传统一性，规范性。
400 telephone, also known as "National Unified Access Code Service", consists of 10 digits. It is a national unified and powerful virtual telephone switchboard designed by telecommunication operators for enterprises and institutions. All calls to this 400 telephone switchboard are transferred to pre-bound entity phones to receive, so as to achieve the unification of enterprise external propaganda. Sex, normative.