ce of Telecom Boundary Clock with assisted partial support (T-BC-A) and Telecom Time Slave Clock with assisted partial support (T-TSC-A) clocks while running G.8275.2 PTPoIP. There is no frequency assistance available across the network in the assisted (T-BC-A and T-TSC-A) cases. Of course, frequency is available from the local source, but G.8273.4 has no test cases for that. The testing methodology is equivalent to the methodology described in the preceding section for testing according to the requirements on G.8273.2, SO the preceding Figure 12-19 is still mostly valid for the test setup. The main difference between these tests and the previous FTS case is that the assisted clocks have two possible reference input signals: the local time source (via 1PPS, for example) as a primary, and a PTP slave port aligned to a remote T-GM over a PTS network. Because the PTP is remote and the 1PPS is local, the PTP input limits are based on the network lim- its at the end of a chain based on G.8271.2, and the 1PPS limits are based on the limits at the begin- ning of a chain. As one example, for the PTP input, the clock must tolerate the noise limit that might appear at the end of the timing chain, whereas it needs to only tolerate 1PPS noise that is gen- erated by a PRTC (at the start of the chain). Figure 12-20 shows possible test topologies for testing T-BC-A clocks. T-BC-A 1PPS Local Ref. T-BC-A PTP Local Ref. Reference Reference Tester input Tester Inputs Synthetic noise injected Synthetic noise injected T-BC-A into the reference signal into the reference signal T-BC-A output T-BC-A output T-BC-A input 1PPS input PTP PRTC T-GM SyncE 10 MHz Timing Timing network network Figure 12-20 Testing T-BC-A Clocks with 1PPS or PTP Inputs As shown in the figure, the new factor is that the T-BC-A (and T-TSC-A) clocks receive a local ref- erence signal from either a local PTP clock (right-hand side) or a PRTC clock via a 1PPS signal (left-hand side). Even though this is a valid setup, G.8273.4 has not yet specified limits for cases w