- This object selects the near end loopback that will be executed upon recognition of a start test. - This object should be ignored if issued while any test is in progress. - line - indicates that the incoming DS3 will be looped back at a point such that the outgoing positive and negative pulses correlate with the polarity of the incoming positive and negative pulses. - payload - indicates that the incoming DS3 payload will be looped back toward the DS3 interface, while the outgoing overhead will be regenerated by a DS3 transmit framer.