Manual

Issue 1, January 2020 Model 348 User Guide
Page 10 Studio Technologies, Inc.
MODEL 348
INTERCOM STATION
If a separate microphone and pair of stereo or
monaural headphones need to be connected
an adapter cable assembly must be fabri-
cated. It would consist of a 5-pin male XLR
connector wired to both a 3-pin female XLR
connector for the microphone and a ¼-inch
or 3.5 mm TRS jack for the headphones. In
this scenario the microphone would, in most
cases, be a dynamic type as the Model 348
provides only low-voltage DC electret power.
Phantom-powered (P12 or P48) microphones
would not be compatible. Most hand-held or
“stick” microphones are dynamic and should
function correctly.
Headset B
The Model 348 also allows direct connec-
tion of gaming headsets that are ubiquitous
in the personal computer world. The 3.5 mm
4-conductor TRRS jack, labeled Headset B, is
compatible with the CTIA™/AHJ configuration
standard which has the headphone left chan-
nel on the tip connection, the headphone right
channel on the ring 1 connection, common
on the ring 2 connection, and the microphone
on the sleeve connection. Compatible head-
sets are readily available, typically described
as personal computer or gaming headsets.
The microphones used in these headsets are
electret type which require a low-voltage DC
source for operation. The Model 348 is able to
provide this power and requires only that the
appropriate setting in the STcontroller person-
al computer software application be selected.
Refer to Figure 3 for a detailed description of
the compatible TRRS plug.
Gooseneck Microphone
A threaded combination bushing/3-conductor
1/4-inch jack is incorporated into the top panel
of the unit. This allows direct connection of the
Studio T
echnologies’ GME-3-12 Gooseneck
Microphone. This unidirectional, electret micro-
phone was designed specifically to maximize
performance in intercom and related applica-
tions. The RTS/Telex/Bosch MCP-90-series is
also directly compatible and will perform well.
The two main requirements for the gooseneck
microphone are that it contain an electret
microphone and the interconnection be in the
form of a ¼-inch 3-conductor plug with inte-
grated threads that have a pitch 7/16-20 UNF.
The 3-conductor ¼-inch jack associated with
the Model 348’s bushing has a tip connection
that is used for both microphone audio as well
as for supplying the low-voltage DC needed
for powering the electret microphone. The ring
connection is used for the microphone low
signal and the sleeve connection is chassis
ground. Within the Model 348’s circuitry the
ring and sleeve connections are connected
together as well as being “tied” (connected)
to the chassis.
The Model 348’s gooseneck bushing includes
a hex head socket set screw with a thread
pitch of 4-40. This allows the gooseneck
microphone to be secured into the bushing
by simply tightening the set screw against the
microphone using a 5/64 hex driver. In many
cases, especially in applications where the
Model 348 will be moved from venue-to-venue,
it will not be optimal for the hex screw to be
utilized. This is because the gooseneck micro-
phone may need to be removed and stored
for transit. In this case the set screw should
be removed and stored.
Figure 3. Headset B (TRRS) connection pinout chart