Datasheet
Introduction
The Model 41 is designed to create broadcast-standard IFB
outputs from line-level audio sources. The unit’s primary
application is to interface analog outputs associated with digi
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tal matrix intercom systems with broadcast IFB user devices.
The Model 41 creates four independent IFB outputs. Each
IFB output provides DC power and two analog audio signals
to support the connected IFB user devices. The Model 41’s
audio quality is excellent; little hiss, hum, or other artifacts
are present. To ensure optimal operation, the unit provides
resources for visually and audibly monitoring the audio output
signals. In addition, the DC output voltage is monitored for
fault conditions.
Installation of the Model 41 is very simple. Audio input con
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nections are made using a 25-pin D-subminiature connector.
The IFB output circuits interface using standard 3-pin XLR
connectors. The compact, one-rack-space package is con
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structed using rugged steel and aluminum components. The
unit’s AC mains power input can range from 100 to 240 volts,
50/60 hertz. This “universal input” ensures correct operation
virtually anywhere in the world.
• Transformer-coupled inputs
• Excellent audio quality
• Superior power-feed performance
• Four independent IFB circuits
• Single (1U) rack-space mounting
• Universal mains input powering
Highlights
Line-Level Audio to IFB Circuit Interface
There may be persons not familiar with the term IFB. That’s
not unreasonable as it’s a somewhat obscure acronym for
interruptible foldback. On its own, the term foldback is an
alternate way of describing a cue or monitor function. Adding
“interruptible” before it means that the cue source can be
temporarily replaced with an audio signal originating from a
producer, director, or other production personnel. IFB outputs
are often used in the broadcast industry for talent cueing
applications, both in studio and field settings.
Both “dry” and “wet” IFB outputs can be deployed and their
characteristics are worth reviewing. The term “dry” IFB typi
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cally refers to a transformer-balanced line-level audio circuit
with a nominal level in the range of 0 to +8 dBu. This is
essentially a standard analog audio circuit that is commonly
used to interconnect audio equipment. The term “wet” IFB
refers to a circuit that combines DC power and one or two
channels of analog audio. The DC power source is typically
in the range of 30 to 32 volts. The audio is unbalanced with
a typical nominal level of –10 dBu. The Model 41 implements
“wet” IFB outputs. As such, in this user guide the term IFB
will always indicate this type of circuit.
IFB outputs provide an effective means of delivering power and
two channels of audio to user devices by means of standard
audio cables. These cables, ubiquitous to the audio industry,
interface using 3-pin male and female XLR connectors. Using
IFB outputs and standard audio cables it’s a simple matter
to support user devices such as listen-only beltpacks 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.
50013-1213, Issue 3