DIN ETS 300205-1995 综合服务数字网络.转呼无应答的补充业务.功能效率和信息流通; 英文版本 ETS 300205:1994
Integrated Services Digital Network (ISDN) - Call Forwarding No Reply (CFNR) supplementary service - Functional capabilities and information flows; English version ETS 300205:1994