Alarm systems - Alarm transmission systems and equipment - Part 1-5: requirements for Packet Switched Network PSN.
报警系统。报警传输系统和设备。第1 - 5部分：包交换网络PS N用要求。
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Chicago’s PSN includes tough gun policing, federal prosecutions and—most important, or so researchers found—meetings with former felons to deter them from returning to crime.