
Configuring WAN Line Services
6-4 117021-A Rev. A
Enabling or Disabling Bipolar with 8-Zero Substitution
T1 uses bipolar format for signals. In bipolar format, alternating positive and
negative pulses on the digital line signify the number 1, and the absence of a pulse
signifies 0 (F
igure 6-2).
Figure 6-2. Bipolar Format
In bipolar format, a negative pulse must always follow a positive pulse, and vice
versa. A long string of 0s on a T1 line would cause the line to lose synchronization
due to lack of pulses. Bay Networks offers bipolar with 8-zero substitution
(B8ZS) for T1 synchronization.
B8ZS substitutes a bipolar violation into a string of eight consecutive 0s at the
transmitting end, and removes the bipolar violation at the receiving end. In a
bipolar violation, the first pulse is in the same direction (positive or negative) as
the previous data pulse (F
igure 6-3).
Line voltage
Data
1 1 100 0 0
0
+3V
-3V
0
LS0009A
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