NT8D14 Universal Trunk card Page 577 of 906Circuit Card Description and InstallationFigure 118Ground start call connection sequence – incoming call from CO/FX/WATSAStateIdleIdleTrunk seizureCall presented toconsole loop keyConsole answersB goes on hookIdleA goes on hookRemarksSignal/directionNear endMeridian1BFar endCOTip open/battery on ringRingingTip open/battery on ringTip open/battery on ringHigh-resistanceloopGround on tip CO grounds tip. Near end detects the groundand makes the trunk busy to all outgoing calls.Ringing is superimposed on battery by theCO.When console answers, near end places alow-resistance loop across the tip and ring.If far end disconnects first, CO removesground from tip. If battery and ground werereversed when call was established, batteryis removed from tip and restored to ring.Near end detects drop in loop current andopens loop.2-way voiceconnectionGround on tip/battery on ringLow-resistance loopHigh-resistance loopHigh-resistance loopWhen CO detects change to low-resistanceloop, it removes ringing. Some COs mayreverse battery and ground on tip and ring.If near end disconnects first, it opens theloop, waits 50 ms, and then reconnects theground detector.CO detects drop in loop current andremoves ground from tip. If battery andground were reversed when call wasestablished, battery is removed from tip andrestored to ring.553-6236
