Nortel Networks Circuit Card - Manual (Page 751)

NTAK79 2.0 Mb PRI card Page 751 of 906
Circuit Card Description and Installation
Switch SW4 – Carrier Shield Grounding
This switch enables for the selective grounding of the Tx / Rx pairs of the
carrier cable. Closing the switch (down position) applies Frame Ground
(FGND) to the coaxial carrier cable shield, creating a 75 ohms unbalanced
configuration. This applies only to the NTBK05CA cable.
Note: The usual method is to ground the outer conductor of the receive
coaxial signal.
Power requirements
The NTAK79 obtains its power from the backplane, drawing maximums of
2 A on +5 V, 50 mA on +12 V and 50 mA on –12 V.
Environment
The NTAK79 meets all applicable Nortel Network’s operating specifications.
Functional description
The NTAK79 card provides the following features and functions:
• recovery of the 2.048 kbps data by the CEPT receiver, at signal levels
which have been attenuated by up 10 dB
• control of CEPT line density using HDB3 which provides 64 kbps clear
channel
• performance monitoring of the receive carrier by means of Bipolar
Violations (BPV), Slips, CRC-4 (CRC), and Frame Bit Errors (FBER)
Table 243
Switch SW4
Switch Down (On) Up (Off)
SW 4-1 Rx – FGND Rx – OPEN
SW 4-2 Tx – FGND Tx – OPEN