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TBE 2730. Trunks Signaling. Trunk groups. TRUNK GROUP TYPES DID – Direct Inward Dial. Digits are passed down the trunk from the C.O. switch to the PBX. The PBX uses those digits to directly route a call to a station instead of having to be transferred by an attendant.
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TBE 2730 Trunks Signaling
Trunk groups • TRUNK GROUP TYPES • DID – Direct Inward Dial. Digits are passed down the trunk from the C.O. switch to the PBX. The PBX uses those digits to directly route a call to a station instead of having to be transferred by an attendant. • TIE – Ties 2 switches together in the same network. • ISDN-PRI – Integrated Services Digital Network/Primary Rate Interface. An ISDN T1. 23B + D. An out of band signaling trunk group. Provides higher data rates and other added services and features. (ie. Caller ID)
Trunks • ANALOG VS. DIGITAL • Analog signals – varied current flow. Wavelike. Older technology. • Digital signal – 1s and 0s. Voltage on and off. T1 or fractional T1 interface. Higher quality of service • Analog and Digital trunks both can provide the same services and features (such as DID) the big difference is that analog trunks are handed off in an analog format. Digital trunks are handed off in a T1 or fractional T1 format (digital).
Trunk Signaling/Addressing • IN-BAND • Loop start – Tip and ring closure. POTS lines/1FBs. Bad way of signaling for a trunk group. • Glare problems with loop start. Glare – when both switches seize the same trunk at the same time. • Ground start – Grounding used as an extra step to prevent glare. Originating switch grounds the ring side. Terminating switch senses ground and closes loop. Originating switch seizes trunk. • Wink Start – onoffhk. Signaling format that supports DID and digit outpulsing. Best way of signaling.
Trunk Signaling/Addressing • OUT-OF-BAND • SS7 – System Signaling No. 7. Used for the PSTN/Carrier networks. Not built to signal to PBX’s. • ISDN-PRI – D channel used to signal for 23 bearer channels. Provides added services and features • PULSING/ADDRESSING • MF – Multifrequency. Used for inband pulsing between carrier switches. Older technology replaced mostly by SS7. • DTMF – Dual Tone Multi-frequency. Use to pulse to customers PBXs.