Studio Technologies 2A 2015 - Manual (Page 20)

Issue 2, March 2015 Model 2A User Guide
Page 20 Studio Technologies, Inc.
the black-colored wire is attached at the
factory to the ring lead of the jack. The oth-
er end should be attached to the – terminal
on the terminal strip. One end of the shield
connection is attached at the factory to the
sleeve of the jack. The other end should
be attached to the SHLD terminal on the
Model 22’s terminal strip. It’s important to
note that a dynamic microphone must not
be connected to the mic terminals; it won’t
provide the correct signal level and dam-
age to the mic may occur.
An external source of talkback audio can
be connected to the Model 22’s terminal
strip. A possible source of this audio would
be a “hot mic” output of an intercom user
station. The line input circuit is electroni-
cally balanced, capacitor coupled, with an
input impedance of 24 k ohms. Balanced
or unbalanced signals can be connected.
An input level trim pot allows signals with
a nominal level range of –15 to +10 dBu to
be correctly interfaced. When connecting
a balanced audio signal it should be con-
nected to the terminal strip’s + and – ter-
minals. The shield wire can be connected
to the SHLD screw terminal associated
with the mic input. Unbalanced signals
may require a bit more attention for cor-
rect operation. The signal high lead should
be connected to the + terminal. The signal
low/shield wire should connect to both the
– terminal and the SHLD terminal. Failure
to make this dual connection can result is
large amounts of hum being induced into
the interrupt signal.
Selecting the Operating Modes
Two slide switches are used to select
the Model 22’s operating modes. The
input select switch allows either the mic
input or the line input terminals of the
5-position terminal strip to be active. In
most cases a Studio Technologies’ Model
11A gooseneck microphone has been
connected. In this case the switch should
be set to its MIC position. If you have con-
nected a signal to the line input terminals,
set the switch to its LINE position. When
the Model 22 is using the line input as its
interrupt audio source an audio trim pot
is active. Adjust that trim pot only after
installing the entire IFB system. Refer to
the Configuration section of this guide for
details on how to set the trim pot.
The Model 22 contains a monitor mute
function which is intended to prevent
acoustical feedback from a loudspeaker
associated with the Model 2A’s monitor
output. When the monitor mute switch is
set to its ON position, the monitor output
will be muted whenever an interrupt (one
or both of the IFB buttons is pressed) on
that access station. When the switch is set
to its OFF position an interrupt from that
specific Model 22 will not cause the moni-
tor output to mute.
Model 24 Access Stations
Up to four Model 24 Access Stations can
be connected to two Model 2A units. In
this way the Model 24 units can provide
remote access to the four IFB channels
associated with the two Model 2As. One
cable, terminated with a male 9-pin D-
subminiature connector (DE-9M) on each
end, links the Model 24 with the Model
2A designated to provide IFB channels 1
and 2. A second identical cable links the
Model 24 with the Model 2A designated to
provide IFB channels 3 and 4. Each Model
24 has an unbalanced microphone input,
a balanced line-level input, five lighted
pushbutton switches, and related circuitry
to access the four IFB channels. Power is