这是itu 关于传真的系列文档，包括t4,t30,t38,v29,v27,v17,v21等-itu This is a series of fax documents, including T3 and T4, t30 and t38, v29, v27, v17, v21, etc.

fax group 3说明,fax group 3 Descr iption