TU-T refers to as equipment limits. This is normally a single clock connected back to back to a test device: input a time signal to the DUT and watch how it behaves or measure what appears at the output. A good example of this is testing a T-BC or Telecom Time Slave Clock (T-TSC) against the G.8273.2 performance recommendation. Network testing to determine the performance of a timing signal at the end of a chain of timing distribution. This form of testing tests the budgeting calculations and allowances in time error (see Chapter 9) to confirm that the synchronization signals meet the requirements when arriving at the final application. Figure 12-8 illustrates these two approaches (for figures in this section, the M and S in circles refer to PTP ports in master or slave mode). PRC/PRS PRC/PRS 10 MHz 10 MHz Timing network Tester Tester 1 PPS 10 MHz PTP + SyncE Figure 12-8 Standalone Equipment Testing (left) Versus Network Testing (right) Each approach is underwritten by a group of ITU-T recommendations, whether it describes a net- work or a clock. Therefore, all the tests relating to the performance on a single node come from a clock recommendation (see "Chapter 8. ITU-T Timing Recommendations", for more information). On the other hand, the network testing comes from ITU-T recommendations on network limits. In the standalone clock test, the DUT is connected back to back to a timing tester. The tester gener- ates timing signals as input to the DUT and compares the output to the generated input. However, in the network test case, there is a chain of network elements involved. To test network performance at the end of the timing distribution chain, the tester might be used to measure the output time signal carried from a remote primary reference time clock (PRTC) and Telecom Grandmaster (T-GM). The test unit can also be used as both input and output if the start and end of the timing chain are co- located. Within each of these test types, the test equipment measures two signals: Frequency testing: Measures the intera