M-AUDIO Delta RBUS - Manual (Page 26)

R-BUS wordclock, and R_BUS PCI if you wish to synchronize internally
with another Delta R_BUS card using the internal hardware connectors
and the supplied cable to connect the two cards.
NOTE: If "S/PDIF In" is selected as the master clock source,
be sure to supply a valid S/PDIF signal to the board’s active
S/PDIF input. Otherwise, erratic timing and/or improper
sample rates will be experienced. The same is true for
selecting "R-BUS In" or “R-BUS PCI” as the master clock
setting – make sure there is a valid R-BUS signal present at
the Delta card’s external or internal R-BUS connector,
respectively.
Once a master clock source has been selected, its synchronization status
is continually monitored and displayed below the master clock radio
buttons. If internal crystal is selected, the status display will always say
"Locked." On the other hand, if S/PDIF In or R-BUS In is selected as the
master clock source, the control panel will display "Locked" only when a
valid S/PDIF or R-BUS signal is detected at the corresponding port. It
will display "Unlocked" when there is no signal at the selected input, or
when the signal is corrupt or invalid for any reason.
Also, when selecting and using S/PDIF In as your master clock setting,
make sure that “S/PDIF” is selected as the input in the “Input Audio
Source” section of the Hardware Settings page. Otherwise, no signal will
be detected at the S/PDIF hardware input.
CODEC SAMPLE RATE
This section indicates the present board sample rate, as set by application
software. The sample rate selected here will be used to drive the digital
mixer and all outputs. The "Rate Locked" checkbox is used to force a
sample rate upon the system. It is disabled by default to allow software
access to all supported sample rates. When checked, it causes the driver
to only operate at the selected sample rate. This means that any
application that attempts to open the Delta R-BUS driver at a sample rate
other than the one selected here will fail to do so and will post an error
message. "Reset Rate When Idle" is selected when you want the sample
rate to return to a particular setting when a software application is not
actively using the board. This is particularly handy for keeping the
digital mixer running at a specific sample rate.
NOTE: Because the digital monitor mixer runs at the sample
rate of the rest of the board, and because sample rate directly
affects frequency response, it may be desirable to keep the
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