DIN EN 300392-12-21-2011 地面中继电系统(TETRA)- 声音加数据(V+D)- 第12部分:补充业务阶段3- 第21分部分:环境监听(AL)(英文版核准本EN 300392-12-21 V1.4.1 (2011-04)作为德国标准)
Terrestrial Trunked Radio (TETRA) - Voice plus Data (V+D) - Part 12: Supplementary services stage 3 - Sub-part 21: Ambience Listening (AL) (Endorsement of the English version EN 300392-12-21 V1.4.1 (2011-04) as German standard)