Principles of Configuring Clocks for the BSC (BM/TC Combined)

This describes the principles of configuring clocks for the BSC when the BM and TC are configured in the same subrack.

GMPS/GEPS Clock

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 of two types: BITS clock and line clock. The BITS clock is more accurate and more reliable. Therefore, it is preferred.

Principles of Configuring Clocks for the BSC

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

**Table 1** Principles of configuring clocks for the BSC
Clock	Configuration Principle
LINE CLOCK	If the GEIUA is configured, a maximum of two line clocks, line clock 0 and line clock 1, can be configured, and the line clock must be configured on the E1/T1 of the A interface in the subrack. If the GOIUA is configured, only one line clock can be and must be configured on port 0 on the GOIUA.
8 kHz reference clock	If the configured line clock signals are selected for the 8 kHz reference clock, do not delete any line clock.
System clock	The principles of configuring the priority of the clock source are as follows: The BSC provides up to four clock source priorities: priority 1 to priority 4, from the highest to the lowest. The clock source and the clock source priority have a one-to-one mapping. By default, the priority of the BITS clock is higher than that of the line clock. By modifying the priority of the clock source, you can set the priority of the line clock higher than that of the BITS clock. 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.