Paradise P300 Change, Rx, Buffer / Clocking, RX Clock Menu, Normal non-Insert Mux operation

If the external 10MHz reference fails totally then it will be automatically replaced with the internal reference. If however it degrades (level, frequency or phase noise), then until it fails totally the modem will continue to use it as the synthesiser reference.

6.7.5Change, Rx, Buffer / Clocking, RX CLOCK Menu

This screen varies depending on the configuration of the Rx path

Normal (non-Insert Mux operation)

This selects the source of the clock which feeds the terrestrial output:

Rx output clock: [?]

1=Sat 2=Tx 3=Internal 4=Station 5=DCE

Change, Rx, Buffer / Clocking, Rx Clock (non-Insert) Menu

Insert Mux operation (generated bearer)

This selects the source of the clock for the PCM BEARER onto which the Rx data is inserted:

Rx output bearer clock source: [?] 1=Sat 2=Tx 3=Internal 4=Station

Change, Rx, Buffer / Clocking, Rx Clock (Insert-Loop) Menu

Insert Mux operation (looped bearer)

This selects the source of the clock for the BACKUP PCM BEARER, which is only used if the normal bearer looped from the Drop Mux fails and the unit auto generates a backup bearer onto which to insert the Rx data. Note that this screen does not display a Tx option, as it is the failure of the Tx bearer input which causes this backup clock to be used in the first place.

Rx o/p bearer backup clk : [?] 1=Sat 2=Internal 3=Station

Change, Rx, Buffer / Clocking, Rx Clock (Insert-Loop) Menu

All the options available on any of these menus for the Rx output clock are as follows:

SATELLITE	The clock from the satellite. This provides `Buffer Disable` operation, the buffer
	size is set to zero and the buffer size menu is no longer available. This is the
	same as `Rx=Rx` clock options found on some other equipment. The Rx PLL
	converts the satellite clock which may include framing and or Reed-Solomon
	overheads back to the rate required at the terrestrial port. If the demodulator
	cannot lock onto a carrier (ie no clock from satellite), then the PLL switches to the
	internal frequency reference to provide a steady clock towards the terrestrial port.
TX CLK IN	The Tx path input clock is turned around to drive the Rx data back to the
	terrestrial. This is normal `Plesiochronous Mode`, and the buffer should be set
	large enough to accommodate both the difference in the clocks at each end of
	the link PLUS the Doppler shift, whilst providing the required interval between
	slips.
	If the Tx & Rx rates are equal then the Tx clock is used directly to clock out the
	Rx data, should the Tx input clock fail the clock is switched to a PLL using as first
	backup the Station Clock if defined as available, or if the Station Clock is defined
	as not available then recovered Satellite Clock (while demodulator remains
	locked). Should this first backup fail it finally falls back to the internal 1PPM

P300H P300 Series Modem Installation and Operating Handbook Page 90