CTC Union FMUX04, Руководство пользователя

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Chapter 1: Introduction
1.7 T1(DS1) Signal Structure
1.7.1 T1 link line rate
The T1 line operates at a nominal rate of 1.544Mb/s.
1.7.2 T1 link line coding
The basic T1 line signal is coded using either the Alternate Mark Inversion (AMI) or B8ZS
rule. In the AMI format, "ones" are alternately transmitted as positive and negative pulses,
whereas "zeros" are transmitted as a zero voltage level. AMI is not used in most 1.544Mb/s
transmissions because synchronization loss occurs during long strings of data zeros.
In the B8ZS format, a string of eight consecutive zeros is replaced with a substitute string of
pulses containing an intentional bipolar violation. The B8ZS code substitutions provide high
pulse density so that the receiving equipment is able to maintain synchronization with the
received signal.
When configured for T1, the 4-CHANNEL T1 Ports support one of two T1 line codes:
AMI
coding.
B8ZS coding.
The 4-CHANNEL T1 Ports support only transparent unframed format. ie. The T1 will pass
through with its original framing structure completely intact.
1.8 Applications / Capabilities
In the following example, the
FMUX04
utilizes an optical fiber connection between a pair of
units to provide 4channels of E1 or T1 between the units. The timing scheme for typical E1 or
T1 equipment is to transparently pass timing from a timing source unit on one side, to a
timing slaved unit on the other. Each of the up to 4 available channels of the
FMUX04 is
independent of any other channel for transparent framing or timing.
Figure 1-2 : Typical Point-to-Point Application of FMUX04
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