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NT8D15 E&M Trunk card Page 661 of 906
Circuit Card Description and Installation
Software service entries
The trunk type is selected by making service change entries in Route Data
Block, Automatic Trunk Maintenance (LD 16). The companding mode is
selected by making service change entries in Trunk Data Block (LD 14).
Refer to Table 208 on page 660 to select the proper values for the trunk type
being employed.
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 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