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2-WIRE IDSL LINE DRIVER RACK CARDS
DCE/DTE Selector for the X.21 Daughterboard
The X.21 daughterboard can be set up as a DCE (default) or DTE device. The
DCE/DTE selector must be installed in the X.21 daughterboard for any
configuration. The following information describes the setting for DCE/DTE.
• DCE setting (default): To set a rack card as a DCE device, install the
DCE/DTE selector with the DCE arrows pointing toward the front panel.
• DTE setting: To set a rack card as a DTE device, install the DCE/DTE selector
with the DTE arrows pointing toward the front panel.
Jumper (JP1) Setting
The X.21 daughterboard operates at speeds up to 2.3 Mbps. When using the
daughterboard at data rates of 2 Mbps or higher, clocking issues may introduce bit
errors. Bit errors can also occur when long cables are used to interconnect the
modem to an X.21 terminal device (router, multiplexor, etc.). To solve bit error
problems due to speed and/or long cables, the X.21 daughterboard is equipped
with a jumper selector (JP1) that changes the sampling edge of the transmit clock.
Refer to Figure 3-24 for jumper JP1 location.
The following is a brief description of JP1 setting and function.
• Normal setting: The jumper shorts the two outer pins of JP1. Figure 3-24 shows
the default position. This position is selected when operating at low data rate
(less than 2 Mbps) and using a short X.21 terminal cable.
• Invert setting: The jumper shorts the two inner pins of JP1. This setting is
selected when operating at data rates of 2 Mbps or higher or when using long
X.21 terminal cables.
NOTE
The G.703 Rear Card module is covered in Appendix D. The 10BASE-T
Ethernet Rear Card module is covered in Appendix E.
