Alesis ADAT-XT20 Reference Manual page 52

Basic Operations: Chapter 4
The CLOCK group of icons indicates which clock source is being used.
The [CLOCK SELECT] button lets you toggle through the various
options, including: INT 48K (internal clock at 48kHz), INT 44.1K
(internal clock at 44.1 kHz) and DIG (external clock source connected to
the [DIGITAL IN] connector on the rear panel). Additionally, if the
XT20 is being used as a slave in a multi-ADAT system, the EXT icon
will light, indicating that the XT20 is deriving its clock from the
master ADAT in the system. See page 59.
The INPUT MON group includes two icons: ALL and AUTO. The ALL
icon will light whenever the All Input function is enabled (by pressing
the [ALL INPUT] button). The AUTO icon will light whenever the
Auto Input function is enabled (by pressing the [AUTO INPUT] button).
See page 50.
The INPUT group of icons indicates which input source is being used.
The ANALOG icon will light whenever the Analog Inputs are selected
(by pressing the [ANALOG INPUT] button). The DIGITAL icon will
light whenever the Digital Inputs are selected (by pressing the
[DIGITAL INPUT] button). The TRK COPY icon will light whenever
the Track Copy function is selected (by pressing the [TRACK COPY]
button). See pages 48 and 49.
This is the Interpolation Indicator. When it flashes, it indicates that
errors have been detected and corrected using an interpolation scheme.
It is a good idea to clean the tape heads and/or make a backup copy of
your tape if you ever see this icon light. See Appendix C for more
information.
16 BIT
20 BIT
This icon lights when there is a 16-bit (Type I) tape inserted in the
transport.
This icon lights when there is a 20-bit (Type II) tape inserted in the
transport.
ADAT XT20 Reference Manual 51