A receiver circuit designed to mute the audio output when the received signal is too weak to provide acceptable audio or, in some cases, when the wrong signal is being received.
(See Noise Squelch, Signal Level Squelch, Tone Coded Squelch)

In wireless, the accuracy to which the operating frequency is maintained as temperature changes over time.

A microphone polar pattern that is similar to the hypercardioid pattern. The supercardioid pattern is slightly less directional and the rear sensitivity lobe is smaller.
(See Hypercardioid)

Used in reference to headphones and means “over the ear.” Can be combined with semi open, closed and open back designs.

The most common implementation of a true diversity receiver, in which the audio from the better of two receiver channels is continuously selected by means of an electronic switch.

A protocol developed by Tascam for transferring up to eight channels of digital audio across a single wire, and hence known as the Tascam Digital InterFace. Originally developed for their Modular Digital Multitrack (MDM) tape machines, TDIF along with the ADAT interface, are the two most popular formats for the transfer of digital audio where more than two tracks of data are involved.

Time Division Multiplexing, a method for putting multiple data streams into a single signal. Originally developed for telephone transmission, Digidesign took the concept, applied it to multi track digital audio and today Pro Tools stands as the de facto standard in the professional audio community.

Total Harmonic Distortion. All electronic devices add some form of distortion to a signal passing through them. In audio, one form of distortion is the addition of harmonics that are not present in the original signal. THD is a measurement of this and is represented as a ratio of the total of all the harmonics added against the original signal at the output of the device.

An optical digital audio format that uses light and fiber optic cables for transmitting data. Similar to S/PDIF data, often the two connectors are found side by side on semi-professional equipment.

Tip, Ring, and Sleeve. A type of 1/4" phone plug that looks like the plug found on stereo headphones. Used in a variety of applications, namely as a balance connector, where the tip and ring both carry the signal, as a send/return connector from an insert of a mixer, and for providing unbalanced stereo connectivity, as in headphones.