This sets whether transmit data is phase-locked to the positive or negative slope of the clock edge on the interface port. An admin adjusts this to resolve data timing issues with connected equipment sensitive to clock edge alignment, though units with onboard G.703 only support the positive-clock-slope setting. For example, an admin troubleshooting intermittent data errors on a non-G.703 port might try switching this from positive-clock-slope to negative-clock-slope to see if it corrects the timing mismatch.