Carrier Interface; Carrier Grounding - Nortel Enterprise 1000 Reference Manual

Page 162 of 236

Carrier interface

Carrier grounding

553-3023-211 Standard 1.00 June 2001
NTBK50 2.0 Mb PRI card
For the E-1 interface, the connection to the external digital carrier is provided
by the line interface chip. This device provides accurate pulse shaping to meet
the CCITT pulse mask requirements. It provides clock recovery functions on
the receive side, as well as tolerance to jitter and wander in the received bit
stream.
Impedance matching (Switch SW2)
The line interface provides for the use of either 75 ohms coaxial or 120 ohms
twisted pair cable. The impedance is selected by SW2, as shown in Table 38.
Table 38
Impedance matching switch settings
Cable Type
75 ohms
120 ohms
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 next to the
bottom left corner of each individual switch.
NTBK50 allows the shield of the Tx and/or Rx pairs of the carrier to be
selectively grounded. Closing (down position) the on-board switch will apply
FGND to the appropriate carrier cable shield. The switch settings are shown
in Table 39 on page 163.
SW 2-1
Down (On)
Up (Off)