 in Chapter 8 for an overview of this ITU-T recommendation. Noise Generation The noise generation of a T-BC-A/T-TSC-A represents the amount of noise produced at the output of the clock when locked to an ideal (wander-free) PTP signal as input. Like the T-BC case, the out- put of a T-BC-A is measured at either the 1PPS output or the PTP master port, whereas the output of a T-TSC-A is measured at the 1PPS output. Table 9-9 summarizes the cTE and dTE that a T-BC-A/T-TSC-A is permitted to generate from within clock. The value of max|TE| for noise generation is for further study. Table 9-9 Maximum Noise Generation of T-BC-A/T-TSC-A Maximum Limits (as defined by ITU-T G.8273.4) Noise Type Class A Class B +50 ns +20 ns 50 ns (peak-to-peak) For further study Source: ITU-T G.8273.4, Table 7.1 Noise Tolerance and Transfer As the T-BC-A/T-TSC-A are taking an input from a local time reference (such as GNSS), obviously the clock must be able to tolerate whatever noise is output from a PRTC. Therefore, the noise that must be tolerated as an input to this clock is set at the same level as the maximum noise that is al- lowed to be generated at the output of a PRTC. Therefore, G.8273.4 specifies that T-BC-A/T-TSC-A must be capable of tolerating input noise with the following specifications: max|TE < 100 ns, the same as the TE limit at the output of a PRTC. Peak-to-peak pktSelected2wayTE < 1100 ns, with a selection window of 200 S and the selection percentage set at 0.25%. Refer to the section "Parameters for Timing Performance" earlier in this chapter for more details on pktSelected2wayTE and other parameters of packet selection. The peak-to-peak is used since the time error will be corrected by the APTS clock, SO the actual value of the offset does not matter. For APTS networks, when the T-TSC-A is external (separate device) to the end application, and where the end application limit is 1500 ns, the T-TSC-A is also expected to maintain max|TEL below 1350 ns at its 1PPS output. This allows for a 150-ns budget in the end applicati