Chapter 3. Configuration61200217L1-1 T3SU 300 User Manual 3-9Transmit ClockSelects the source of the clock used to transfer data from the DTE tothe T3SU 300. Use the following chart to determine your selection:Configuration Selections for DSX-1 InterfacesThe configuration selections listed in Table 3-3 are available forQuad DSX-1 interfaces. Separate selections can be made for each ofthe four DSX-1 ports of the card. This menu is shown in Figure 3-5.CD Selects the control mode for the carrier detect (CD) lead.F ORCED O N: The CD lead remains active at all times.O FF WHEN OOS/OOF: The CD control lead remains on unless theT3SU 300 receives an OOS/OOF condition from the network.T RANSMIT C LOCK See the following section for a description of this item.Table 3-2. Additional V.35 Interface Port Configuration SelectionsSelection DescriptionSelect... If...Normal you want the transmit clock to be derived from theT3SU 300.Invert your DTE device cannot provide a transmit clocksignal and data errors are present between your DTEand the T3SU 300.External you are transmitting at high rates. This selectioneliminates data errors caused by excessive delays inthe DTE transmit clock receiver, transmit data driver,and cable length.Selecting Normal or Invert clocking options depends on your DTE, cablelength, and cable characteristics. To verify error free operation, perform aDTE loopback test and a BERT test from the DTE. See the chapterDiagnostics on page 6-1 for information on performing these tests.
