The source of Transmit Clock. 'loopTiming' or 'loopback' indicates that the recovered receive clock is used as the transmit clock.

'localTiming' or 'internal' indicates that a local clock source is used or when an external clock is attached to the box containing the interface.

'throughTiming' or 'external' indicates that recovered receive clock from another card or interface is used as the transmit clock.

'adaptive' indicates that the clock is recovered according to the received data flow rate.

'master' and 'fallback' values may be used RO to indicate active clock.

'station' - indicate clock received from station port is used as transmit clock.