e T-BC (for T-TSC it is limited to the 1PPS signal). Note that the noise generated at the physical frequency output is affected only by the physical layer frequency in- put (covered in Chapter 5). The noise generated is defined by three parameters, cTE, dTE, and max|TE|, and the maximum lim- its for T-BC/T-TSC at both PTP and 1PPS outputs are summarized in Table 9-6. Note that for fur- ther study means that the ITU-T is studying those details but has not produced agreement on the actual value. It can stay in that state for some time. Table 9-6 Maximum Noise Generation of T-BC/T-TSC Noise Maximum Limits (as defined by ITU-T G.8273.2) Class A Class B Class C Class D 100 ns 70 ns 30 ns 5 ns (max TEL For further +50 ns +20 ns +10 ns study 40 ns For further 40 ns (MTIE) 10 ns (MTIE) (MTIE) study 4 ns (TDEV) 2 ns (TDEV) (TDEV) For further For further 70 ns 70 ns study study The limits specified are for measurements at constant temperature. Noise Tolerance Noise tolerance defines how much noise a slave clock can receive (tolerate) on its input and still be able to maintain its output signal within the specified performance limits. Tolerance for noise is in- dicated by the clock continuing to function normally when receiving a noisy input. Conditions used to determine when the clock is continuing to behave normally include when the clock Is not raising any alarms Is not switching to a new reference input Does not move into holdover state As shown in Figure 9-26, the input signals for T-BC/T-TSC are the PTP port and physical frequency input. To test tolerance, an input noise is generated on these interfaces (dots), and the clock is mon- itored to ensure it correctly tolerates the input noise. T-BC/T-TSC Time & (for T-BC only) Noise @ PTP phase slave master recovery Local oscillator Noise @ frequency Frequency recovery Figure 9-26 Noise Tolerance of a T-BC and T-TSC For PTP input, there is no requirement for cTE tolerance because the PTP slave by itself is not able to identify or detect cTE. To do SO requires additional in