User manual

For example, when channel framing is PCM30 or PCM30C (with time slot number is 30 and first time slot is 1) refer to the

following graphic. When Pass Through is set Off, the DSL transfer data will not include the time slots of FAS and CAS. The

information of FAS and CAS on remote is re-created.

Warning: When the E1 is carrying signaling information for voice, do NOT set pass through Off. Pass through must be set to

ON or signaling and other information will be lost.

Setup E1 Parameter, Line Code

The G.SHDSL .Bis NTU supports two different line codings. HDB3 is the most popular and preferred line coding and is also the

default setting. AMI line coding is also selectable.

HDB3

In this line coding, the transmitter substitutes a deliberate bipolar 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 minimize pulse density

requirements. Unless AMI is required for 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 one and zero. One

is sent as pulse, and zero is 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 data stream will cause problems, since

the NTU receiving the signal relies on the signal to recover the 2048kbps clock.