Focusrite Scarlett 18i20 USB-C Audio/MIDI Interface (3rd Generation) - Manual (Page 12)

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8. Input meters – eight 5-segment LED bargraph meters indicating the signal levels of the eight
analogue input signals. The meters show signal level after the input gain stage, and thus
their indication is affected by the gain controls. The LEDs illuminate at -42 (green, “signal
present”), -18 (green), -6 (green), -3 (yellow) and 0 dBFS (red). A level of 0 dBFS implies digital
clipping, and should always be avoided.
9.
USB active LED – a green LED which illuminates when the unit is recognised by the
computer to which it is connected.
10. Locked – a green LED which confirms clock synchronisation, either to the Scarlett 18i20’s
internal clock or to an external digital input.
11. MIDI LED – green LED, illuminates when MIDI data is received at the MIDI IN port.
12. MONITOR – main monitor output level control: this will normally control the level at the main
monitor outputs on the rear panel, but can be configured in Focusrite Control to adjust the
level at any of the unit’s ten analogue outputs.
13. DIM and MUTE – two switches controlling the 18i20’s monitor outputs; DIM reduces the
output levels by 18 dB, while MUTE turns the outputs off. By default, these switches affect
the MAIN monitor outputs 1 and 2, but may be configured in Focusrite Control to act on any
of the analogue outputs. The switches each have an associated LED (DIM: yellow, MUTE: red)
indicating that the function is selected. Note that DIM and MUTE may also be selected from
Focusrite Control.
14. Talkback microphone
15. TALKBACK – press and hold this button to activate talkback. When active, ‘TALKBACK’
illuminates green, and the talkback mic [14] may be routed to the 18i20’s various outputs.
By default, talkback routes to the two headphone outputs [17], but the routing may be
configured in Focusrite Control to feed any desired combination of outputs. Note this button
is ‘momentary’ – talkback is only active while it is pressed. Talkback may also be activated
from Focusrite Control.
16. ALT – when the ALT function is enabled in Focusrite Control, pressing this button diverts
the main monitor mix from MAIN LINE OUTPUTS 1 and 2 to ALT LINE OUTPUTS 3 and 4.
Connect a pair of secondary monitor speakers to the ALT outputs, and select ALT to switch
between your main monitors and the secondary pair. ‘ALT’ illuminates green when selected.
This function may also be selected from Focusrite Control. (Note that when ALT is enabled,
the line outputs not in use are muted: e.g., to use Line Outputs 3 and 4 for another purpose,
first unmute them in Focusrite Control.)
17. Headphone volume 1 and 2 – connect one or two pairs of stereo headphones at the two
¼” (6.25 mm) TRS jack sockets below the controls. The headphone outputs always carry
the signals that are currently routed to analogue outputs 7/8 and 9/10 (as stereo pairs) in
Focusrite Control.
18. POWER – AC power switch.