Mackie PROFESSIONAL MIC/LINE MIXERS WITH FX AND USB I/O PROFX16 Owner's Manual page 27

TRS Send/Receive Insert Jacks
Mackie's single-jack inserts are the three-conductor,
TRS 1⁄4" phone type. They are unbalanced, but have
both the mixer output (send) and the mixer input
(return) signals in one connector. See Figure F.
ring
(TRS plug)
tip sleeve
This plug connects to one of the
mixer' s Channel Insert jacks.
Figure F
The sleeve is the common ground (earth) for both
signals. The send from the mixer to the external unit is
carried on the tip, and the return from the unit to the
mixer is on the ring.
Using the Send-only on an Insert Jack
If you insert a TS (mono) 1⁄4" plug only partially (to
the first click) into a Mackie insert jack, the plug will
not activate the jack switch and will not open the insert
loop in the circuit (thereby allowing the channel signal
to continue on its merry way through the mixer).
This allows you to tap out the channel signal without
interrupting normal operation.
If you push the 1⁄4" TS plug in to the second click, you
will open the jack switch and create a direct out, which
does interrupt the signal in that channel. See Figure G.
NOTE: Do not overload or short-circuit the signal you
are tapping from the mixer. That will affect the internal
signal.
MONO PLUG
Direct out with no signal interruption to master.
Insert only to first "click."
MONO PLUG
Direct out with signal interruption to master.
Insert all the way in to the second "click."
STEREO
PLUG
For use as an effects loop.
(TIP = SEND to effect, RING = RETURN from effect.)
Figure G
SEND to processor
"tip"
"ring"
RETURN from processor
Channel Insert jack
Channel Insert jack
Channel Insert jack
Owner's Manual 27