Nortel Networks Circuit Card - Manual (Page 664)

Page 664 of 906 NT8D15 E&M Trunk card
553-3001-211 Standard 3.00 August 2005
Applications
The optional applications, features and signaling arrangements for each trunk
are assigned through unique route and trunk data blocks. Refer to the
Features and Services (553-3001-306) for information about assigning
features and services to trunks.
PAD switching
The transmission properties of each trunk are characterized by
class-of-service (COS) assignments in the trunk data block (LD 14). The
assignment may be non-Via Net Loss (non-VNL) or via Net Loss (VNL). To
ensure stability and minimize echo when connecting to long-haul VNL (Tie)
trunks, non-VNL trunks are assigned either Transmission Compensated
(TRC) or Non-Transmission Compensated (NTC) class-of-service.
The TRC and NTC COS options determine the operation of the switchable
pads contained in the trunk circuits. They are assigned as follows:
• TRC for a two-wire non-VNL trunk facility with a loss of greater than
2 dB or for which impedance compensation is provided, or for a
four-wire non-VNL facility.
• NTC for a two-wire non-VNL trunk facility with a loss of less than 2 dB
or when impedance compensation is not provided.