Nortel Networks Circuit Card 311 - Manual (Page 929)

Physical description 929
Switch SW2 - Carrier Impedance Configuration
This switch sets the carrier impedance to either 120 ohms or 75 ohms.
Twisted pair cable is usually associated with 120 ohms. Coaxial cable is
usually associated with the 75 ohms setting.
Table 380
Switch SW2
Cable Type SW 2-1 SW 2-2
75 ohms Up (Off) Down (On)
120 ohms Down (On) Up (Off)
Switch SW3 - Clock Controller Configuration
This switch enables/disables (H/W) the on-board Clock Controller. Disable
the SW 3-2 if the on-board clock controller is not in use.
Table 381
Switch SW3
Switch Down (On) Up (Off) Note
SW 3-1 — — Spare
SW 3-2 Disabled Enabled
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.
Table 382
Switch SW4
Switch Down (On) Up (Off)
SW 4-1 Rx – FGND Rx – OPEN
SW 4-2 Tx – FGND Tx – OPEN
The usual method is to ground the outer conductor of the receive coaxial
signal.The NTAK79 card incorporates four on-board dip switches. The
tables that follow provide information on the various settings and related
functions of these switches.
Note: The ON position for all the switches is towards the bottom of the
card. This is indicated by a white dot printed on the board adjacent to
the bottom left corner of each individual switch.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008
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