Nortel Meridian 1 Option 11C Compact Technical Reference Manual

Contents

Chapter 12 — NTMW44 Universal Trunk Card Page 123 of 136Meridian 1 Option 11C Compact Technical Reference GuideApplicationThe optional applications, features, and signaling arrangements for eachtrunk are assigned through route and trunk data blocks.Loop start operationLoop start operation is configured in software. When the Universal Trunk isidle, it provides a high impedance toward the CO for isolation and ACdetection. The alerting signal is 20 Hz ringing sent by North American CO.When an incoming call is answered, ringing is tripped when the trunk placesa low resistance DC loop towards the CO.For outgoing calls from a telephone set or attendant console, software sendsan outgoing seizure message to place a low resistance loop across the Tip andRing leads towards the CO. When the CO is ready to receive digits, it returnsdial tone. The outward address signaling is applied from the system in theform of DTMF tones or dial pulses.Ground start operationGround start operation is configured in software. In an idle state, the Tipconductor from the CO is open and a high resistance negative battery ispresent on the Tip of the trunk. This biases the Tip ground detector OFF untilthe CO places ground on the Tip at seizure. After the Tip ground is detected,the NTMW44 scans for a ringing detection signal before presenting the callto an attendant and tripping the ringing. A low resistance is placed across theTip and Ring conductors and a speech path is established.Direct Inward Dial operationAn incoming call from the CO places a low resistance loop across the Tip andRing leads. Dial pulses or DTMF signals are then presented from the CO.When the call is presented and the terminating party answers, the NTMW44reverses battery and ground on the Tip and Ring leads to the CO. The trunkis arranged for first party release. The CO releases the trunk by removing thelow resistance loop and normal battery and ground are restored at the system.