Loopback Adapters and Crossover Cables for T1 and DDS Circuits
Loopback adapters and crossover cables are useful tools for troubleshooting both DDS & T1 circuits. This document shows the necessary pinout for building them.
Where is Pin 1?
Figure 1 shows a how to orient a standard RJ-45 to RJ-45 silver satin cable to determine pin 1. There are eight pins total in a RJ-45 connector.
Figure 1
T1 Loopback Adapter
Figure 2 shows the pinout for building a T1 loopback adapter. This pinout is the same for both a RJ-45 plug and RJ-45 jack.
Figure 2
T1 Crossover Cable
Figure 3 shows the pinout for building a T1 crossover cable. This cable can be used to connect two T1 CSU/DSU (i.e.,TSU) products in a back-to-back configuration.
Figure 3
DDS Loopback Adapter
Figure 4 shows the pinout for building a DDS loopback adapter. This pinout is the same for both a RJ-45 plug and RJ-45 jack.
Figure 4
DDS Crossover Cable
Figure 5 shows the pinout for building a DDS crossover cable. This cable can be used to connect two DDS CSU/DSU (i.e., DSU) products in a back-to-back configuration.
