Mitel Sx 200 El/ml Technicians Handbook
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Troubleshooting and Repair 71 Troubleshooting Loop Start Line/Trunk The Loop Start Line/Trunk serves the standard domestic applications and small businesses that have key systems and PBX applications. Figure 13: Loop Start Line/Trunk Table 6: Loop Start Line/Trunk Summary SignalLoop Start Line PBX OutgoingLoop Start Line PBX Incoming SeizeTip-Ring leads activated (shorted); Loop Current flows in line90Vac is applied to Ring lead in 2 sec on, 4 sec off cadence Seize AcknowledgmentLoop Current and/or dial tone generated - DigitsLoop Current toggled (Rotary) or DTMF - Stop Dial - - (Sheet 1 of 2)

Technician’s Handbook 72 Test/Verify (Loop Start) Verify far-end (CO) circuits by using a standard telephone set in place of the Loop Start trunk circuit. Verify near-end (PBX Loop Start) circuits by connecting to a local PBX ONS circuit. Check for appropriate voltages on Tip-Ring in each call state. During off-hook condition, 18 mA DC minimum should be drawn from the CO (typical 25-40 mA). Some Key/PBX systems may be polarity sensitive; reverse Tip-Ring to verify. Receipt of DigitsAudible Tones - Busy, Reorder, Ringback dependent upon digits dialed and called party condition - Answer SupervisionSome COs can reverse current flowTip-Ring leads activated (shorted); Loop Current flows in line Disconnect SupervisionNear- end termination: PBX/Telephone can break Loop CurrentNear- end termination: PBX/Telephone can break Loop Current Table 6: Loop Start Line/Trunk Summary (Continued) SignalLoop Start Line PBX OutgoingLoop Start Line PBX Incoming (Sheet 2 of 2)

Troubleshooting and Repair 73 Troubleshooting Ground Start Trunk The Ground Start Trunk serves most PBX-CO connections in an analog environment. Figure 14: Ground Start Trunk Table 7: Ground Start Trunk Summary SignalGround Start Trunk PBX OutgoingGround Start Trunk PBX Incoming SeizeRing lead goes active. PBX grounds the ring leadTip lead goes active; 90 Vac is applied to Ring lead in 2 sec on, 4 sec off cadence Seize AcknowledgmentTip lead goes active; Audible Dial Tone generated; ground returned on tipTip-Ring leads activated (shorted); Loop Current flows in line DigitsLoop Current toggled (Rotary) or DTMF - (Sheet 1 of 2)

Technician’s Handbook 74 Test/Verify (Ground Start) Verify the far-end (CO) circuits by using a standard telephone for incoming calls. Verify outgoing calls by using a Butt Set with a ground- start lead (momentarily shorting the ring lead to the ground will produce a dial tone from the far end). Verify the near-end (PBX Ground Start) circuits by connecting to known working far end Ground Start circuits. Verify that appropriate voltages are present on Tip-Ring in each call state. During off-hook condition, 18 mA DC minimum should be drawn from the CO (typical 35-40 mA). Tip-Ring is polarity sensitive. PBX will be unable to initiate calls if reversed. Reverse polarity to verify. Stop Dial - - Receipt of DigitsAudible Tones - Busy, Reorder, Ringback dependent upon digits dialed and called party condition - Answer SupervisionCO reverses current flow in Tip-Ring Disconnect SupervisionNear-end: PBX opens loop Far-end: CO removes ground from ring Near or Far-end termination: Loop Current is broken Table 7: Ground Start Trunk Summary (Continued) SignalGround Start Trunk PBX OutgoingGround Start Trunk PBX Incoming (Sheet 2 of 2)

Troubleshooting and Repair 75 Troubleshooting Direct Inward Dial (DID)/Loop Trunk You use the Direct Inward Dial (DID)/Loop trunk primarily in analog DID applications; rarely in PBX-PBX Loop Tie trunk applications. This trunk uses current reversal to signal supervision information and provides digit flow capability in both directions, when the trunk is in the loop/tie mode. Figure 15: Direct Inward Dial (DID)/Loop Trunk

Technician’s Handbook 76 Table 8: Direct Inward Dial/Loop Trunk Summary SignalDID/Loop Trunk PBX OutgoingDID/Loop Trunk PBX Incoming SeizeTip-Ring leads are activated (shorted); Loop Current flows in lineTip-Ring leads are activated (shorted); Loop Current flows in line Seize AcknowledgmentImmediate Dial - Tip-Ring leads stay active Outgoing Wink - Tip-Ring leads toggle Loop Current direction Delay Dial - Tip-Ring leads reverse Loop Current following seizure; reverse again when ready to goImmediate Dial - Tip-Ring leads stay active. Incoming Wink - Tip-Ring leads toggle Loop Current direction DigitsLoop Current toggled (Rotary) or DTMFLoop Current toggled (Rotary) or DTMF Stop DialTip-Ring leads reverse Loop Current direction; forward again when ready - Receipt of DigitsAudible Tones - Busy, Reorder, Ringback dependent upon digits dialed and called party conditionAudible Tones - Busy, Reorder, Ringback generated and sent to calling party dependent upon digits received and state of called party Answer SupervisionCurrent flow in Tip-Ring is reversedCurrent flow in Tip-Ring is reversed Disconnect SupervisionNear or Far-end termination: Loop Current broken Near or Far-end termination: Loop Current is broken

Troubleshooting and Repair 77 Troubleshooting Test/Verify (DID) Verify the far-end circuits by the use of a standard telephone for outgoing calls. Verify the near-end circuits by connecting to known working DID/Loop circuits. Verify that appropriate voltages are present on Tip-Ring in each call state. During off-hook condition, 20-25 mA should be drawn from the far-end. Ear & Mouth (E&M) Trunk You use the E&M trunk in Tie Trunk applications. The E&M trunks support all the signaling information. The Tip-Ring is used in a 2-wire operation shown in Figure 12 - E&M Trunk - Type I (2-wire) on page 78. The Tip-Ring and Tip Rx-Ring Rx is used in a 4-wire operation shown in Figure 13 - E&M Trunk - Type V (4-wire) on page 79. Type I Type 1 is used in applications when a telephone company is providing a transmission path between PBXs. The E&M circuits connect to Telco-provided Signaling circuits, which prepare the E&M signals for long distance use. Each end is identical to the other; all required voltage translation is provided by the cable carrier. Type 1 may be used in a 2-or 4-wire operation.

Technician’s Handbook 78 Figure 16: E&M Trunk - Type I (2-wire)

Troubleshooting and Repair 79 Troubleshooting Type V Type V is used in applications where short distance direct back-to-back operation is desired. The M-lead invert is required at both ends. Figure 17: E&M Trunk - Type V (4-wire) Table 9: E&M Trunk Summary SignalE&M Trunk PBX OutgoingE&M Trunk PBX Incoming SeizeM lead goes active (voltage is dependent on Type I or Type V operation)E lead goes active Seize AcknowledgmentImmediate Dial - E Lead stays idle. Outgoing Wink - E Lead toggles active/idle. Delay Dial - E Lead goes active following M; goes idle when ready to goImmediate Dial - M Lead stays idle. Incoming Wink - M Lead toggles active/idle (Sheet 1 of 2)

Technician’s Handbook 80 Test/Verify (E&M) Loop back to self whenever more than 1 E&M type V circuit is available. Verify far-end circuits by activating near-end M lead and listening for far- end dial tone. Verify near-end circuits by activating near-end E lead and listening for near-end dial tone. Verify that appropriate voltages are present on E&M leads in each call state. DigitsM toggles (Rotary) or DTMF through audio pathE toggles (Rotary) or DTMF through audio path Stop DialE lead goes active; goes inactive when ready to go - Receipt of DigitsAudible Tones - Busy, Reorder, Ringback dependent upon digits dialed and called party conditionAudible Tones - Busy, Reorder, Ringback generated and sent to calling party dependent upon digits received and called party condition Answer SupervisionE lead goes activeM lead goes active Disconnect SupervisionNear-end termination: M lead goes inactive; E follows Far-end termination: E lead goes inactive; M follows Near-end termination: M lead goes inactive; E follows Far-end termination: E lead goes inactive; M follows Table 9: E&M Trunk Summary (Continued) SignalE&M Trunk PBX OutgoingE&M Trunk PBX Incoming (Sheet 2 of 2)