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Switch SW2
A detailed description of each switch (SW1-1 through SW1-5) setting fol-
lows the summary table below:
Switch SW2-1 Line Coding: HDB3 (default).
Use Switch SW2-1 to control the Network Line Coding options. Set
these options to be the same as the Line Coding given to you by your
Service Provider. If you are using two Model 2701/Is together as short
range modems, set both units to HDB3.
Options: HDB3, AMI
HDB3 In this line coding, the transmitter substitutes a deliberate bipo-
lar violation when excessive zeros in the data stream are
detected. The receiver recognizes these special violations and
decodes them as zeros. This method enables the network to
meet minimum pulse density requirements. Unless AMI is
required in your application, HDB3 should be used whenever
possible.
AMI Alternate Mark Inversion defines a pulse as a “mark,” a binary
one, as opposed to a zero. In an E1 network connection, signals
are transmitted as a sequence of ones and zeros. Ones are
sent as pulses, and zeros are sent as spaces, i.e., no pulse.
Every other pulse is inverted from the previous pulse in polarity,
so that the signal can be effectively transmitted. This means,
however, that a long sequence of zeros in the data stream will
SW2-1 Line Encoding
Off HDB3
On AMI