NT1R20 Off-Premise Station Analog Line card Page 171 of 906Circuit Card Description and InstallationOutpulsing Addressing signals Near-end station dials number (looppulsing or DTMF tones).The system detects start of dialing andremove dial tone.Ringback (or busy) The system decodes addressing, routecalls, and supply ringback tone tonear-end station if far-end is on-hook.(Busy tone is supplied if far-end isoff-hook).Two-way voiceconnectionWhen call is answered, ringback tone isremoved, and call is put through tofar-end station.Near-end stationhangs-up firstHigh resistance loop If near end station hangs-up first, theline card detects the drop in loopcurrent.Line card unit idle Group on tip, battery on ringHigh resistance loopLine card unit is ready for the next call.Far end stationhangs up firstHigh resistance loop If the far-end hangs-up first, the systemdetects disconnect signalling from thetrunk. The person at the near-endrecognizes the end of the call andhangs-up.Line card unit idle Ground on tip/battery on ringHigh resistance loopLine card unit is ready for the next call.Table 69Call connection sequence—near-end station receiving call (Part 2 of 2)StateSignal / DirectionFar-end / Near-end Remarks
