s it particu- larly recent, and increasing political pressure is being applied to address it. Power industry members are addressing this concern through a combination of several approaches: Improving the resilience and accuracy of the GNSS receivers they deploy as PRTC as sources for their substation automation, phasor measurement units (PMU), and supervisory control and data acquisition (SCADA) systems around the grid. Using the transport network to carry timing signals from other remote GNSS + T-GM sites to improve the dispersion of their time sources over a wider area to survive localized outages. Looking at using a limited number of atomic sources to increase the holdover capability of their reference clocks. This allows them to increase the autonomy for the timing signal sources for their monitoring and control systems. To implement this strategy, as covered in Chapter 2, utilities are working on projects to deploy PTP telecom profiles across the WAN to supply redundant timing signals in the case of localized outages of their timing sources. This solution is robust and is increasingly deployed in several other indus- tries as well. The unique issue to address is that when the PTP timing signal using the telecom profile reaches the substation, there needs to be a device that can handle the interworking between the telecom profile used for the WAN and the Power Profile inside the substation. In Power Profile terms, this is known as a boundary clock-one that can recover the clock over the WAN from the remote T-GM and provide a signal to the Power Profile transparent clocks inside the substation. Many primary sources already located in the substation can increasingly support being a slave to the telecom profile. This is exactly what the interworking function needs to do. See Figure 9-39 for an illustration. PTP G.8275.1 with SyncE Interworking function PRTC / T-GM Interworking Interworking function function Substation network Substation power profile power network power profile profile Primary GNSS source Figure