Nortel Enterprise 1000 Reference Manual page 128

Page 128 of 236
553-3023-211 Standard 1.00 June 2001
NT8D15 E&M Trunk Card
Port-to-port loss configuration
Loss parameters are selected on the E&M trunk card by a switchable pad
controlled by CODEC emulation software. The pads settings are called "in"
and "out." Pad settings are determined by the three factors listed below: the
first two are under direct user control; the third is controlled indirectly.
• Class of Service is assigned in LD 14.
• Facility termination is selected (2-wire or 4-wire) in LD 14 (the 2-wire
setting provides 0.5 dB more loss in each direction of transmission for
echo control).
Note: Facilities associated with the Nortel Networks Electronic
Switched Network (ESN) are recommended to be 4-wire for optimum
transmission; thus, the 4-wire setting is generally referred to as the ESN
setting. However, the 4-wire setting is not restricted to networks using
the ESN feature. Conversely, the 2-wire setting, often called non-ESN,
can be used on certain trunks in an ESN environment.
• Port-to-port connection loss is automatically set by software on the basis
of the port type selected in LD 16; only the port type is set by the user.
The transmission properties of each trunk are characterized by the class of
service assigned in LD 14. Transmission properties can be Via Net Loss
(VNL) or non-Via Net Loss (non-VNL).
The VNL class of service is assigned at the CLS prompt by typing VNL. The
non-VNL class of service is assigned at the CLS prompt by typing TRC
(Transmission Compensated) or NTC (Non-Transmission Compensated).
Non-VNL trunks are assigned a TRC or NTC class of service to ensure
stability and minimize echo when connecting to long-haul trunks, such as tie
trunks. The class of service determines the operation of the switchable pads
contained in each unit. They are assigned as follows:
• TRC for a 2-wire non-VNL trunk facility with a loss of greater than
2 dB, or for which impedance compensation is provided, or for a 4-wire
non-VNL facility
• NTC for a 2-wire, non-VNL trunk facility with a loss of less than 2 dB,
or when impedance compensation is not provided