output interfaces. This test resembles the noise transfer test for EEC clocks as it tests the characteristics and performance of the passband filter. The criteria to pass is that in the passband, the phase gain of the DUT should be smaller than 0.1 dB. SyncE to PTP and SyncE to 1PPS transfer, which measures the transfer of phase wander from the physical frequency interface to the phase/time outputs. This test also resembles the previous test as it tests the passband filter. The tester generates a series of input wander at different frequencies, both outside and inside the range of the passband. There are different criteria for Class A/B versus Class C/D clocks because of the difference in the upper limits of the bandpass filter (1-10 Hz versus 1-3 Hz). But the result is the same; the phase gain inside the passband should be smaller than 0.2 dB. Transient response (response in the packet layer to a physical layer transient): This (short) test involves adding a transient to the SyncE frequency signal and monitoring the response on the packet layer. The tester generates a transient that includes a degraded QL value (for about 13 s) to indicate loss of traceability with a return to a normal signal after that. There is a mask from G.8273.2 that defines the limits on the TE measured. Again, the clock requires some settle time before the test is executed. Holdover, or long-term transient: Measures phase error under two conditions. One is when the PTP input has been removed but the SyncE is still available. The second is when both sig- nals are removed. For G.8273.2 compliance testing, only the first case applies, as the behavior with loss of both signals is for further study. The tester can perform this test standalone with the DUT, although many operators prefer to do it when the DUT is getting its signal from a network. The metrics consist of the dTE with low- pass filter applied and an MTIE mask for both constant and variable temperature indicating pass/fail. The values are 62-123 ns MTIE after 1000 S with the consta