This attribute indicates the source of time used by the grandmaster clock. Options: 1.atomicClock(16) - indicates that any device, or device directly connected to such a device, that is based on atomic resonance for frequency and that has been calibrated against international standards for frequency and, if the PTP timescale is used. 2.gPS(32) - indicates that any device synchronized to a satellite system that distribute time and frequency tied to international standards 3.terrestrialRadio(48) - indicates that any device synchronized via any of the radio distribution systems that distribute time and frequency tied to international standards 4.ptp(64) - indicates that any device synchronized to a PTP-based source of time external to the domain 5.ntp(80) - indicates that any device synchronized via NTP or Simple Network Time Protocol (SNTP) to servers that distribute time and frequency tied to international standards 6.handSet(96) - indicates that used for any device whose time has been set by means of a human interface based on observation of an international standards source of time to within the claimed clock accuracy 7.other(144) - indicates that other source of time and/or frequency not covered by other values 8.internalOscillator(160)- indicates that any device whose frequency is not based on atomic resonance nor calibrated against international standards for frequency, and whose time is based on a free-running oscillator with epoch determined in an arbitrary or unknown manner Default: gPS(32)