Studio Technologies 41 2004 - Manual (Page 5)

Issue 1, October 2004 Model 41 User Guide
Page 6 Studio Technologies, Inc.
IFB circuits provide an effective means
of delivering power and two channels of
audio to user devices by means of stan-
dard audio cables. These cables, ubiqui-
tous to the audio industry, interface using
3-pin male and female XLR-type connec-
tors. With IFB circuits and standard audio
cables it’s a simple matter to support user
devices such as listen-only belt packs and
announcer’s consoles with no external
power source required. Whether 100 or
1000 feet apart, reliable operation can be
provided.
In many cases, the Model 41 Interface will
be used in on-air television applications.
Whether installed in a fixed location or as
part of a remote facility, excellent perfor-
mance can be obtained. In addition, the
Model 41 is applicable for non-broadcast
applications. For example, audio record-
ing and post-production facilities can also
effectively use the unit. Combined with
stereo or mono listen-only belt packs,
also available from Studio Technologies,
a variety of headphone cue systems can
easily be deployed. As the Model 41’s
audio inputs are compatible with standard
line-level audio signals virtually any analog
source can be connected.
Four Independent IFB Circuits
The Model 41 supplies four independent
IFB circuits. Each circuit consists of two
audio inputs and a “wet” IFB output cir-
cuit. The audio inputs are transformer
coupled, have a nominal level of +4 dBu,
and are compatible with balanced or
unbalanced sources. In on-air television
broadcast applications the audio sources
will often be analog outputs from matrix
intercom systems. Two sources are typi-
cally designated to feed user cue signals
to stereo or monaural headsets or head-
phones. Generally one source is config-
ured in the matrix intercom system as
“interrupt” while the other is configured as
“program.” An alternate term often used
for the “interrupt” channel is “program-
with-interrupt.” This may be more descrip-
tive as the function is actually a program
source that gets interrupted with talkback
audio. The “program” channel is typically
a continuous source of program audio.
An alternate term is “program-only.” For
other applications, the Model 41’s audio
inputs can be connected to a 2-channel
or stereo audio source. This configuration
may prove useful in radio broadcasting,
audio-with-picture, or recording studio
applications.
Maintaining excellent audio performance
was a major Model 41 design goal—the
hiss, hum, and noise associated with
typical IFB circuits was simply not accept-
able. The Model 41 meets those require-
ments with audio that is “on-air” quality:
low distortion, high signal-to-noise ratio,
and ample headroom. On-air talent and
guests, production personnel, and techni-
cians will all appreciate the clean, quiet
cue signal.
The Model 41’s IFB circuits provide DC
power and two channels of unbalanced
audio over a single 3-conductor output.
The DC output is nominally 30 volts with
a maximum rated current of 200 milliam-
peres. A major strength of the Model 41
is the IFB circuit’s ability to effectively
deliver DC power over a variety of condi-
tions. Unlike other interface devices that
use a common but less-than-ideal circuit
topology, a unique IFB circuit was devel-
oped by Studio Technologies to achieve
the desired performance goals. The re-
sult is a major improvement in effectively