Home / Standards / GB 3971.2-1983 GB 3971.2-1983 Abolished Interoffice junction digital line signalling system for telephone automatic switching network 电话自动交换网局间中继数字型线路信号方式 Standard Type GB ICS 33.040.30 CCS M12 Status 废止 Issue Date 1983-12-15 Implementation 1984-10-01 Responsible Dept 工业和信息化部（通信） Drafting Unit N/A