Tascam PCI-822 User Manual page 18

If the PCI-822 sample rate is almost the same as the incoming audio
clock, but not perfectly locked, the Slip indicator flashes red
periodically. A slash appears across the green indicator until you click
'Clear Errors.' See "Synchronization" later in this Guide for more
details about slip errors.
The TDIF and SPDIF inputs are mapped directly to the recording
devices (T 1:2, T 3:4, T 5:6, T 7:8, and S 1:2) that you'll use within
your audio applications.
The 'Channels In Use' indicators show activity on each input channel.
If an input channel is open or in use, its indicator is bright red.
— Digital Output Status —
This section shows which output channels are active. When an output
channel is playing data, its indicator is bright green.
— Hardware Status (Macintosh only) —
On the Macintosh, this section displays status information about the
PCI-822 hardware.
PCI-822 User's Guide 15