Writing a DS0 channel number, 1 through 24 matching a T1's timeslots, into this object places that specific DS0 into a far-end loopback, looping traffic back at the remote end so the admin can test the circuit path without a technician on-site. An admin troubleshooting a specific timeslot writes that channel's number here rather than looping the entire T1, isolating the test to just the suspect DS0. For example, writing the value 7 loops timeslot 7 back at the far end so the admin can check for bit errors from the near end using a test set, without disturbing the other 23 channels.