Studio Technologies 220 2008 - Manual (Page 33)

Model 220 User Guide Issue 4, October 2008
Studio Technologies, Inc. Page 33
two colors in the opposite fashion. Their
choice is to have the red LED lit whenever
the main output is active, warning the tal-
ent that they are “on-air.” The green LED
is lit whenever the main output is muted,
indicating to the talent that it’s “safe” to
say whatever they wish, about whomever
they wish to say it about!
For consistency, the LED associated with
each talkback button was selected to be
green. They light whenever their associ-
ated talkback output is active. It’s possible
that some applications may benefit from
revising these LED colors too. While red
is certainly one possible choice, other col-
ors are also a possibility including amber,
orange, or blue—these days there are lots
of choices available. The only limitation
is the amount of current available to light
each LED. Using series resistors of no less
than 560 ohms will ensure correct Model
220 operation.
A qualified technician can easily revise the
LED colors to meet an application’s exact
needs. The process would begin by disas-
sembling the Model 220’s enclosure and
detaching the pushbutton/LED printed cir-
cuit board assembly. The LEDs would then
be unsoldered, removed, and reinstalled
(or replaced) in the desired locations. To
control the LED current and set the bright-
ness, a resistor is electrically in series with
each LED. An 820 ohm, ¼-watt resistor is
associated with the red LED while a 560
ohm, ¼-watt resistor is associated with
each green LED. These resistors would
also have to be unsoldered, removed, and
reinstalled. Then the unit would be reas-
sembled and tested to confirm that the
changes function as desired.
For additional information about chang-
ing the LED colors, please contact Studio
Technologies technical support.
Travel Case
For portable applications it may be desir-
able to store and transport each Model
220 in a protective case. After much travel
with prototype announcer console units,
Studio Technologies’ personnel learned
to appreciate the Pelican Model 1450
case. Purchased with the foam interior
option, it does an excellent job of holding
one Model 220, its associated 24 volt DC
power supply, and documentation. Some
applications may benefit from selecting a
larger case that would also hold a related
headset, cables, etc. A larger case could
also be selected that would hold multiple
Model 220 units. Pelican sells their prod-
ucts through a dealer network, many of
which can be located via a web search.
Connecting Line-Level Audio
to the IFB Input
In “emergency” situations it’s possible to
connect line-level audio signals directly
to the Model 220’s IFB input connector.
This can be successfully done as long as
several limitations are taken into account.
The first limitation is that the 10 k ohm
input circuit presents an unbalanced load
to the source. In most cases this shouldn’t
pose a problem. If a balanced intercon-
nection scheme must be maintained an
in-line isolation transformer can be used.
A second limitation is that the audio level
presented must not exceed 0 dBu or
signal “clipping” may occur. Prepare a
3-pin male XLR-type connector so that the
line-level audio source designated as IFB
channel 1 is connected with signal high
on pin 2 and low/shield on pin 1. The
audio source designated as IFB channel
2 should be connected with signal high
on pin 3 and low/shield on pin 1. With
this connection scheme the nominal input