DIN EN 50136-2-4-2000 警报系统.警报传输系统和设备.第2-4部分:使用公共交换电话网络带声音通信器的系统设备的要求
Alarm systems - Alarm transmission systems and equipment - Part 2-4: Requirements for equipment used in systems with voice communicators using the public switched telephone network; German version EN 50136-2-4:1998