This read-only enumerated value reports the source of the DS3/E3 interface's transmit clock as loopTiming(1), localTiming(2), or throughTiming(3), where loop timing derives from the recovered receive clock of another DS3 interface. An admin checks this to confirm the interface's clock synchronization source, important for troubleshooting timing-related errors in a DS3/E3 network. A value of loopTiming(1) tells the admin this interface derives its transmit clock from the recovered clock of another DS3 interface rather than from a local or network clock source.