Studio Technologies 41 2007 - Manual (Page 6)

Issue 2, February 2007 Model 41 User Guide
Page 6 Studio Technologies, Inc.
IFB circuits provide an effective means of
delivering power and two channels of au-
dio to user devices by means of standard
audio cables. These cables, ubiquitous to
the audio industry, interface using 3-pin
male and female XLR-type connectors.
Using 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 the IFB
source and user devices are 100 or 1000
feet apart, reliable operation can almost
always 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, the unit is capable
of providing excellent performance. In
addition, the Model 41 is applicable for
non-broadcast applications. For example,
audio recording and post-production
facilities can also effectively use the Model
41. Combined with stereo or mono listen-
only belt packs, also available from Studio
Technologies, a variety of headphone
cue systems can easily be deployed. And
since 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 2-channel “wet” IFB
output. 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 in-
tercom systems. Two sources are typically
designated to serve as user cue signals.
Generally one source is configured in
the matrix intercom system as “interrupt”
while the other is configured as “pro-
gram.” 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 ste-
reo audio source. This configuration may
prove useful in radio broadcasting, audio-
with-picture, or recording studio applica-
tions. The specific application will dictate
whether both cue signals will be utilized
by the end user. In on-air sports broadcast
situations a “double-muff” (stereo) head-
set will provide a user with both audio
channels, one for each ear. In interview or
news-gathering applications it’s common
to use a single “earpiece” to provide a
user with program-with-interrupt audio.
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