er Pull-in/Hold-in Wander Phase Level Level Accuracy Stability Range Filtering Transient G.811.1 +1 x 10-12 Applicable G.811 +1 x 10-11 Applicable +1.0 x 10-10 MTIE < G.812 Type II +1.6 x 10-8 +1.6 x 10-8 0.001 Hz 150 ns +2.7 x 10-9 MTIE <1 G.812 Type I Not defined +1.0 x 10-8 0.003 Hz / day G.812 Type +1.2 x 10-8 MTIE <150 +4.6 x 10-6 +4.6 x 10-6 0.001 Hz 3.0 Hz G.812 Type +3.7 x 10-7 MTIE <1 +4.6 x 10-6 +4.6 x 10-6 0.1 Hz SONET G.813 Opt 1 +2.0 x 10-6 MTIE <1 +4.6 x 10-6 +4.6 x 10-6 1-10 Hz +4.6 x 10-6 MTIE <1 G.813 Opt 2 20 x 10-6 +20 x 10-6 0.1 Hz / day Not defined +32 x 10-6 +32 x 10-6 Not defined Defined MTIE <1 Not defined +32 x 10-6 Not defined +32 x 10-6 Not defined A source of frequency, such as a PRC/PRS, will need to output some form of reference frequency signal for the downstream clocks to use as an input to guide their own oscillators. This is commonly a sine wave. More information on this signal is provided on 2-MHz and 10-MHz frequency signals in the following section "Sources of Frequency." Frequency, Phase, and Time Clocks When the topic moves from frequency to phase and time synchronization, the clock that provides the reference signal of frequency, time, and phase synchronization for other clocks in the network or a section of a network is known as the primary reference time clock (PRTC). The addition of the word "time" should give a hint that this source clock is phase and time aware, and not just a highly stable form of frequency. A PRTC normally consists of some form of GNSS receiver, which may also be mated with a highly accurate PRC/PRS autonomous frequency source. The autonomous source is normally some form of atomic clock and provides an extended accurate holdover should the GNSS signal be interrupted. This is the function of the GNSS receiver, allowing traceability to a source of UTC that can also be used to calibrate the time on the atomic clock. A standalone, autonomous atomic clock can be a PRTC, but first it needs some form of calibration to align it to UTC, because a source of fr