NTBK50 2.0 Mb PRI card Page 769 of 894

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 246.

Table 246

Impedance matching switch settings

Cable Type

SW 2-1

 

 

75 ohms

Down (On)

120 ohms

Up (Off)

 

 

Note: The ON position for all the switches is toward 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.

Carrier grounding

NTBK50 enables the shield of the Tx and/or Rx pairs of the carrier to be selectively grounded. Closing (down position) the on-board switch applies FGND to the appropriate carrier cable shield. The switch settings are shown in Table 247.

Table 247

Carrier Shield grounding switch settings

Switch

Down (On)

Up (Off)

 

 

 

SW 4 – 1

Rx – FGND

Rx – OPEN

 

 

 

SW 4 – 2

Tx – FGND

Tx – OPEN

 

 

 

Circuit Card Description and Installation

Page 769
Image 769
Nortel Networks 553-3001-211 manual Impedance matching Switch SW2, Impedance matching switch settings Cable Type