Private Telecommunication Network (PTN); Inter-exchange signalling protocol; Do not disturb and do not disturb override supplementary services
专用电信网(PTN);交换间信令协议;请勿打扰和请勿打扰覆盖补充服务
Do not disturb and do not disturb override supplementary services at Q. See DTR/ECMA-0002 (ECMA-TR/SVC) for service description. See ENV41005 for definition of stage 3. See ENV41004 for definition of Q reference point. To contain PICS proforma.