User manual

Chapter 1. Introduction
8 Version 1.2 Apr 2006
1.4 E1 Signal Structure
E1 link line rate
The E1 line operates at a nominal rate of 2.048Mb/s.
E1 link line coding
The basic E1 line signal is coded using either the Alternate Mark Inversion (AMI) or HDB3
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 2.048Mb/s transmissions
because synchronization loss occurs during long strings of data zeros.
In the HDB3 format, a string of four consecutive zeros is replaced with a substitute string of
pulses containing an intentional bipolar violation. The HDB3 code substitutions provide high pulse
density so that the receiving equipment is able to maintain synchronization with the received signal.
The 4-CHANNEL E1 Port Card supports two E1 line codes:
AMI coding.
HDB3 coding.
The 4-CHANNEL E1 Port Card supports only transparent unframed format. ie. The E1 will
pass through with its original framing structure completely intact.
1.5 T1(DS1) Signal Structure
T1 link line rate
The T1 line operates at a nominal rate of 1.544Mb/s.
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.
The 4-CHANNEL T1 Port Card supports two T1 line codes:
AMI coding.
B8ZS coding.
The 4-CHANNEL T1 Port Card supports only transparent unframed format. ie. The T1 will
pass through with its original framing structure completely intact.