Digi 90031300 manual Four-Wire Direct Wiring, Four-Wire Direct Daisy Chain Cable Wiring

Four-Wire Direct Wiring

Four-Wire Direct wiring connects T1 Modem Bank units where longer synchronous cable runs are necessary. While not as fast as Eight-Wire connections (the maximum data transfer rate is 1.8 megabaud1), this wiring method is more economical, and is sufficient in all but the most demanding high-performance applications. This means that terminal users should see no degradation in performance. In the Four-Wire Direct wiring mode, the clock signals are encoded with the receive and transmit data signals, so only two twisted pairs are required. The Four-Wire Direct cable is a twisted pair cable with a male HD-15 (high-density DB-15) connector at one end and a female HD-15 at the other end. The cable should be shielded, and the shield must be connected to the HD-15 connector shell at both ends. See Figure 34.

Figure 34 Four-Wire Direct Daisy Chain Cable Wiring

1If each T1 line transmits at 1.544 Mbit/second, only one T1 Modem Bank can be connected to this line and still maintain the full data rate. See Table 8 on page 96 for restrictions on cable lengths.

Appendix E 95