
Configuring Line Services
2-22 115391-A Rev. A
Bipolar Format
T1 and E1 use bipolar format for signals. In bipolar format, alternating positive
and negative pulses on the digital line signify the number one, and the absence of
a pulse signifies zero (F
igure 2-10). A negative pulse must always follow a
positive pulse, and vice versa.
Figure 2-10. Bipolar Format
A long string of zeros on a T1 or E1 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 zeros 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 2-11).
Line voltage
Data
11 10000
0
+3V
-3V
0
LS0009A
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