Cabletron Systems CSX1000 - Manual (Page 97)

Workgroup Remote Access Switch 97
C ONFIGURING R ESOURCES AND L INES
Lines
D IGITS V ERIFIED
The number of digits to verify (starting at the rightmost digit), so that when the system receives a
phone call it can determine on which bearer to accept the phone call. The maximum number of
digits should be 7, which is the default value in most cases.
F RAMING T YPES
For primary rate lines only. The normal line transmission method employed on a PRI line is a time-
division multiplexed (TDM) scheme of repeating fixed-length frames. For T1 lines, of each frame,
a single bit is used to convey such things as a frame alignment pattern, data checksums, and in more
advanced networks, maintenance commands, between the network and the Customer Premise
Equipment (CPE). For E1 lines, all of channel 0 is used for this. The two most common framing
types for PRI/T1 lines are SF and ESF, which are 12- and 24-frame formats, respectively. E1 lines
can use one of three framing types: doubleframe, multiframe with no CRC, or multiframe with
CRC, with the most common being multiframe CRC.
L INE E NCODING
For Primary Rate lines only. Line encoding specifies the nature of the signals that are used to
represent binary one and zero at the physical layer. Two encoding methods are Alternate Mark
Inversion (AMI) and Bipolar 8 Zero Substitution (B8ZS). AMI as the encoding scheme implies that
the applications using the transmission line must guarantee a certain number of 1s in the signal to
help prevent a loss of synchronization in the network. This is possible if the voltage level of the
signal remains zero for too long a period of time (i.e., too many logical 0s in the transmitted data).
B8ZS enforces no such limits on the application using the transmission medium since it introduces
bipolar violations in the signal. These violations are in turn interpreted at the receiving end not as
errors, but simply as the substitution of a 1 for a 0 after certain number of consecutive 0s were
detected in the transmitted signal.
S IGNALING M ETHOD
For primary rate lines only. The signaling method dictates how and where the call signaling is to
be carried. The two methods available are Common Channel and Robbed Bit Signaling.
C OMMON C HANNEL
In the Common Channel signaling case, one of the 24 channels of the PRI frame is devoted
to call control messaging.
R OBBED B IT S IGNALING
Robbed Bit Signaling is not supported for the CyberSWITCH.
L INE B UILD O UT
For primary rate lines only. No matter what the quality of the cabling employed in a network, each
and every line experiences some signal loss or degradation. Line Build Out describes the degree of
attenuation to be applied to the transmission signal in order to have the correct signal levels and
shape arrive at the receiver. Generally, the longer the line connecting the CPE and the network
equipment, the less the transmitted signal is attenuated.
CFGEDIT will use short or long haul information to determine the correct Line Build Out (i.e.,
degree of attenuation) for your lines. The value you input (in CFGEDIT) to determine attenuation
depends on whether or not you are using an external Channel Service Unit (CSU).
If you are using an external CSU, you will specify a value under Short Haul Build Out. Specify the
length of the line, in meters, from CPE to the CSU by selecting a range from zero to 210 meters.