Public Switch Telephone Network is one of mature networks.
公共交换电话网是成熟的网络之一。
This invention refers to public telephone, data exchanging network system engineering tech.
本发明属于公用电话、数据交换网系统工程技术。
This invention refers to public telephone, data exchanging network system engineering tech.
本发明属于公用电话、数据交换网系统工程技术。
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