E-Carrier, G.703 [wip]

E1-Carrier is a synchronized telecom tech. which uses TDM.
An E1 frame is divided into 32 Timeslots of 64Kbps each. (8 bits sampled 8000 times a second = 64Kbps)

Timeslots 0 - 31



Physical Interface
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Balanced: 120ohm 2 pair twisted wire. RJ-48 (1,2,4,5) and 8P8C connector.
Unbalanced: 75ohm coax pair. Uses BNC connectors.

Logical Presentation
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Unframed G.703: Allows usage of full bandwidth. 2.048Mbps for E1, 1.544Mbps T1.
Framed G.703: Spec defined by G.704. Timeslot 0 is used for framing, timing, synchronization and alarm signalling. Timeslot 16 is used for Signalling. The rest of the timeslots can be defined to carry data or be idle. There is also the option of using CRC-4.

Line Encoding
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This is the method of physically putting 1s and 0s on the wire. These operate on Layer 2.
HDB3, High-Density Bipolar 3, mostly used in Europe
AMI, B8ZS is used in Nort America.

Clock Source
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You can either use clocking from the line, which is provided by your Telecom Company, or internally generated clock of your router/csu-dsu.


Good Introduction to G.703
The FAQs of Life About G.703 @ Patton