传真通信国家标准，相当于ITU - T T.30协议。文件传真三类机在电话网中的互通技术条件　第2部分：在公用电话交换网上的文件传真传输规程-fax communications standards, equivalent to the ITU-T 7-9-2 agreement. Three categories of documents by fax machine telephone network in the exchange of technical conditions Part 2 : the Public Switched online documents by fax transmission order