Glossary of Professional Audio and Music Terms
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Diversity Receiver - In wireless microphone systems, one of the biggest problems is the frequency of "drop-outs", where the strength of the RF signal present at the receiver becomes too low for stable operation. This causes the system to produce extraneous noise rather than clean signal. One solution to the problem is to use two separate antennae (spaced slightly apart) on the receiver. The receiver constantly compares the incoming RF signals to determine which antennae is providing the stronger signal. The receiver is constantly comparing to see which antenna is providing the better signal, and can quickly switch from one to the other as signal strength changes. This system works more reliably than systems using a single antennae, but is not as stable as true diversity systems.
Dropout - When using a wireless mic system, a dropout is an area where the radio frequency (RF) carrier reception falls below a usable level, which usually causes the receiver to mute (no audible output). See "squelch". However, some older wireless receivers will emit loud "white noise" - like the sound of an old radio tuned between stations.
FireWire - also known as IEEE 1394, Firewire is a high speed data exchange protocol developed at Apple. It is now a common interface on digital video equipment and digital audio interfaces. FireWire is s a hot swappable technology and allows 63 devices on a buss with auto termination and identification. FireWire now exists in two variations FW400 (400Mb/sec) and FW800 (800Mb/sec).
Squelch - A function found on some wireless microphone systems that allows the user to set the receiver to mute or gate itself when the carrier falls below a specified level. This control was a very important part of wireless systems for many years, but with modern technology there are more sophisticated and automated methods of handling these things. The manual squelch control is being progressively eliminated from many modern systems.
Thunderbolt - an I/O technology that supports high-resolution displays and high-performance data devices through a single, compact port. Thunderbolt began at Intel Labs with a simple concept: create an incredibly fast input/output technology that just about anything can plug into. After close technical collaboration between Intel and Apple, Thunderbolt emerged from the lab to make its appearance in the new MacBook Pro and the new iMac. Intel co-invented USB and PCI Express, which have become widely adopted technologies for data transfer. Apple invented FireWire and was instrumental in popularizing USB. Their collective experience has made Thunderbolt the most powerful, most flexible I/O technology ever in a personal computer.
True Diversity Receiver - In wireless microphone systems, one of the biggest problems is the frequency of "drop-outs", where the strength of the RF signal present at the receiver becomes too low for stable operation. Diversity receivers have two separate antennae and the receiver selects the signal from the antennae with the strongest signal at any time. A true diversity system is a more advanced system in which the receiver has two independent receiver sections. A comparison circuit constantly polls the two receivers and selects the strongest signal. The result is an exceptionally stable signal, since the appearance of a dropout in both antennas at the same time is not likely under normal circumstances.
Wireless Receiver - A wireless system consists of two main components: a transmitter, and a receiver. The function of the receiver is to pick up the radio signal broadcast by the transmitter and change it back into an audio signal. Receivers are available in two primary designs. Single antenna receivers utilize one receiving antenna and one tuner, similar to an FM radio. Diversity receivers, or dual antenna systems, usually provide superior wireless microphone performance as they use two two antennae and select the most powerful signal at any time - thus reducing, or eliminating "dropouts".
Wireless Transmitter - A wireless system consists of two main components: a transmitter, and a receiver. The transmitter converts the audio signal into a radio signal and broadcasts it as a radio wave via an antenna. Transmitters are available in two basic types: "bodypack" or "belt pack" and "handheld". The "body-pack" or "belt-pack" is a small box about the size as a pack of playing cards. The transmitter clips to the user's belt or may be worn on the body. In the case of a handheld wireless microphone, the transmitter is built into the body of the microphone, resulting in a wireless mic that is only slightly larger than a standard wired microphone. Usually, a variety of microphone elements or "heads" are available for handheld wireless microphones.