In this tab, the different synchronisation options for RM4200D are configured.

You can set the System Sample Rat to 48 kHz or 44,1 kHz.

	Important
	Even if the RM4200D works with external synchronisation, you must adjust the correct sampling rate here, since otherwise the internal quartz PLL can not lock properly to the external clock.

You can define the two synchronisation sources Sync Source 1 and Sync Source 2. The option configured under Sync Source 1 is the primary synchronisation source. If this fails, the system automatically switches to the source configured under Sync Source 2. If this also fails, the system switches to the internal clock of 48 kHz or 44,1 kHz.

The following options are available for synchronisation:

Configuration of the module in Slot 10	Configuration in Slots 1-8	Available Sync Source 1, 2	Function
RM420-848M or RM420-848L or RM420-848M + RM420-424S	At least one Digital I/O Module RM420-111	Internal	Internal synchronisation source 48 kHz or 44,1 kHz.
		AES <Slot.Port:Label>	Synchronisation is generated from the incoming AES data, if the AES signal on this input is valid.
		BNC	TTL wordclock input 48 kHz or 44,1 kHz.
RM420-848M + RM420-421S	At least one Digital I/O Module RM420-111	Internal	Internal synchronisation source 48 kHz or 44,1 kHz.
		AES <Slot.Port:Label>	Synchronisation is generated from the incoming AES data, if the AES signal on this input is valid.
		BNC	TTL wordclock input 48 kHz or 44,1 kHz.
		MultiChannel	The synchronisation is generated from the incoming MADI data stream if a valid MADI signal is attached.
RM420-848M + RM420-422S	At least one Digital I/O Module RM420-111	Internal	Internal Sync source 48 kHz or 44,1 kHz.
		AES <Slot.Port:Label>	Synchronisation is generated from the incoming AES data, if the AES signal on this input is valid.
		BNC	Important This option can not be used, since the BNC socket is not available for space reasons!
		MultiChannel MADI 1	The synchronisation is generated from the incoming MADI data stream of MADI port 1 (top) if a valid MADI signal is attached.
		MultiChannel MADI 2	The synchronisation is generated from the incoming MADI data stream of MADI port 2 (bottom) if a valid MADI signal is attached.
RM420-848M+RM420-422S Option for redundant MADI (see Redundant MADI)	At least one Digital I/O Module RM420-111	Internal	Internal Sync source 48 kHz or 44,1 kHz.
		AES <Slot.Port:Label>	Synchronisation is generated from the incoming AES data, if the AES signal on this input is valid.
		BNC	Important This option can not be used, since the BNC socket is not available for space reasons!
		MultiChannel	The synchronisation is generated from the incoming MADI data stream of MADI port 1 (top) if a valid MADI signal is attached.If the MADI signal on port 1 is invalid, the system switches to port 2 (bottom) automatically if a valid MADI signal is available there.

	Note
	If you configure a digital input of a RM420-111 module as synchronisation source, it is irrelevant, if this input has its sample rate converter activated or not. (see also DSP Frame I/O — Configuring the DSP Frame)

Important

Please consider the following restrictions when connecting the RM4200D to external synchronisation sources: In order to make the Quartz PLLs used for external synchronisation work correctly, the external clock signals must work stable in a range of ±75 ppm around the selected sampling rates of 48 kHz or 44,1 kHz respectively. External synchronisation signals can only be connected to the slots 1 to 10, synchronisation using the slots 11 to 30 is not possible! If MADI interfaces are used, the interconnected systems must use the same clock signal! If three modules RM420-422 are used together, they can only be synchronized from MADI, AES3/EBU or internally. This is caused by the fact that on the module RM420-422 (Dual -MADI) there is no space for a BNC socket.

With the checkbox Slot 10 BNC as Output the function of the BNC socket on slot 10 is determined. If this option is active, the BNC socket on slot 10 works as TTL wordclock output. This is only possible if none of the two synchronisation sources uses the option BNC. In this case, the BNC socket works as an input!

In contrast, the BNC sockets of the slots 20 and 30 are always defined as TTL wordclock outputs and can e.g. synchronise local sources. Basically, all TTL wordclock outputs, all AES3/EBU digital outputs and all MADI outputs work with the same system sample frequency, depending on configuration and status of Sync Source 1 and Sync Source 2.

In a DSP frame with several DSP modules, each module uses its own synchronisation. In this case the modules in backplane 2 and 3 synchronise themselves to the module in backplane 1 as “Master”. Under most circumstances, this works without problems and you do not need to worry about it.

However, if the DSP frame uses several backplanes and at least one external synchronisation source simultaneously, things are a bit different: On rare occasions and under certain circumstances there can be synchronisation problems, when the synchronisation source is switched.

If you experience such effects, activate the checkbox Disable VCXO on BP2/3. This disables the quartz PLL on backplanes 2 and 3, which increases the tolerance for synchronisation. Activate this option, if you need to minimize distortions on the outputs of backplanes 2 and 3 when switching the synchronization source.

Important

Backplane 1 is always the synchronisation “Master”, backplanes 2 and 3 are “Slaves” and need to synchronize themselves to the Master. If backplane 1 itself gets its synchronisation from an external source and this source fails, it will switch over to its second synchronisation source, Sync Source 2. After that, the backplanes 2 and 3 in turn need to synchronise themselves again, but only after the signal on backplane 1 has become stable again. This whole process takes some time. While backplane 1 is switching its synchronisation source and stabilizing itself again, the audio links between backplane 1 and 2 and backplane 1 and backplane 3 are cut. This happens only for a few milliseconds, until the system has synchronized itself again completely. During this time, distortions may happen on the audio links and the DSP frame may give warning messages about the state of the audio links. Also, D/A converters and AES3/EBU outputs on backplanes 2 and 3 may output distortion noise. The reason for that is the re-synchronisation of the system. The Option Disable VCXO on BP2/3 shortens the time necessary for this process by setting the PLL to a much shorter adjustment time than usual. However, you should activate this option only if the DSP frame contains more than one backplane, if it is synchronized from an external signal and if you are experiencing problems when switching synchronisation. If this is not the case, do not change anything!

Activate the checkbox Varispeed, to synchronize the systems to an external clock with a variable frequency between 40 kHz and 48,2 kHz.