Principles of Configuring Clocks for the BSC (A over IP)

This describes the principles of configuring clocks for the BSC in A over IP mode.

The GGCU in the GMPS traces the upper-level clock, and then provides clock signals for the GMPS and the GEPS.

The reference clock for the GGCU is the BITS clock.

Table 1 lists the principles of configuring clocks for the BSC.

**Table 1** Principles of configuring clocks for the BSC
Clock	Configuration Principle
8 kHz reference clock	In A over IP mode, the clock source for the BSC cannot be the line clock.
System clock	The principles of configuring the priority of the clock source are as follows: The BSC provides up to two clock source priorities: priority 1 and priority 2. Priority 1 is higher than priority 2. The clock source and the clock source priority have a one-to-one mapping. The strategies of switching the clock source are as follows: The BSC in operation requires only one clock source. You need to select the strategy of switching the faulty clock source to a normal clock source. The clock source has three working modes: automatic, manual, and self-oscillation. In automatic mode, you do not have to specify a clock source as the current clock source. The BSC automatically selects a clock source with the highest priority. For example, if the current clock source of priority 3 is faulty, the BSC selects the clock source of priority 4. After the faulty clock source recovers, the BSC switches back to the clock source of priority 3. If all the clock sources are faulty, the BSC switches to the HOLD OVER mode. When the clock source recovers, the BSC switches to the self-oscillation mode. In manual mode, a clock source is specified as the current clock source. The BSC cannot automatically switch to another clock source even if this clock source fails. The self-oscillation mode is the default clock working mode of the BSC.