Nortel Networks Circuit Card User Manual

 NTAK79 2.0 Mb PRI card

The line interface provides for the use of either 75 ohms coaxial or 120 ohms 
twisted pair cable. The impedance is selected by a switch, as shown in
Table 245.  

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. 

The NTAK79 card provides the capability of selectively grounding the shield 
of the Tx and/or Rx pairs of the carrier. Closing (down) the on-board switch 
applies FGND to the appropriate carrier cable shield. The switch settings are 
shown in Table 246.  

The receiver extracts data and clock from an AMI (Alternate Mark Inversion) 
coded signal and outputs clock and synchronized data. The receiver is 
sensitive to signals over the entire range of cable lengths and requires no 
equalization. The clock and data recovery meets or exceeds the jitter 
specifications of the CCITT recommendation G.823, and the jitter attenuation 

75 ohms

S2

S1

120 ohms

S1

S2

S4-1

Rx shield

Open

GND

S4-2

Tx shield

Open

GND