Page 586 of 906 NT8D14 Universal Trunk card553-3001-211 Standard 3.00 August 2005Figure 124DID trunk, loop DR call connection sequence – incoming call from COAStateIdleIdleTrunk seizureOutpulsingA ringsB goes on hookIdleA goes on hookRemarksSignal/directionNear endSystemBFar endCOHigh-resistanceloopAddress signalingHigh-resistance loopHigh-resistance loopGroundon tip/batteryon ringGround on tip/battery on ringGround on tip/battery on ringLow-resistance loop CO places a low resistance between tip andring.Near end detects increase in loop currentand makes trunk busy to all outgoing calls.CO applies addressing to the trunk in theform of battery-ground or loop pulses orDTMF tones.Near end detects addressing, alerts terminalA, and provides ringback tone to CO.If far end disconnects first, CO opens theloop.Near end detects drop in loop current andreverses battery and ground on tip and ring.2-way voiceconnectionBattery on tip/ground on ringRingbackWhen terminal A goes off hook, near endtrips ringback tone and provides answersuper-vision by reversing battery and groundon tip and ring.If near end disconnects first, it reversesbattery and ground on tip and ring.CO detects battery/ground reversal andopens loop.553-AAA1138
