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Clocking.HBus.ClockSource

Value	Description
`OSC`	Causes the board to drive the bus clock using its on-board oscillator. This setting should only be used when specifying the clock master. It should be used only if no external timing reference is available (from a digital trunk or other source).
`A_CLOCK`	Causes the board to take its timing reference from the `CT_C8_A` and `CT_FRAME_A` timing signals on the H.100 bus. Since these signals are driven by the clock master, a board with the setting is a clock slave.
`NETREF`	Causes the board to drive the bus clock based on NETREF. NETREF is a clock signal broadcast on the bus by another device, based (usually) on an external timing reference. Note: This setting should only be used when specifying the clock master. Rather than making a QX board the clock master based on a reference signal from another board, NMS recommends making that board the clock master.