Line-Level Audio to IFB Circuit Interface 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 digital 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 connections 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 constructed 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. 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 typically 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. 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 mobile facility, the unit is capable of providing excellent performance. In addition, the Model 41 can be used 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 beltpacks, 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. Features: Transformer-coupled inputs Excellent audio quality Superior power-feed performance Four independent IFB circuits Single rack-space mounting Universal mains input powering
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