The Studio Technologies Model 42A 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 42A creates four independent IFB outputs. For convenience, the four outputs can be connected by way of eight 3-pin male XLR connectors; four of which are located on the back panel and four on the front.
Installation of the Model 42A 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 V, 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 V. The audio is unbalanced with a typical nominal level of -10 dBu. The Model 42A 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.