The glossary pages provide definitions for over 2680 PA-related terms. If you can't find the term you are looking for, or would like any of the existing definitions to be expanded, please email me − likewise of course if you find any errors in the links etc. Use of this information is conditional upon acceptance of the Disclaimer on the PAforMusic home page.
The definitions for these terms are given on the assumption of their use in the context of PA systems; many of the terms have more general meanings when used in a wider context. Where more than one definition is given for a term, the definitions are numbered (1), (2) etc.
Some of the definitions themselves use terms (such as "signal") in a specific way − most of these are links (just the first time they are used, in each definition), so just click on them to see the meanings that are intended.
Two miniature sizes of this style of jack are available, having sleeve diameters of 3.5 mm and 2.5 mm respectively (known respectively as 1⁄8″ and 3⁄32″ in the USA, though these dimensions are only approximate). Both of these sizes are available in mono (2-pole) and stereo (3-pole) versions and are most commonly used for connections to personal music players and to computer sound cards and laptops. The 3.5 mm size is frequently referred to as a 'mini-jack'.
A more recent innovation is a 4-pole version of the 3.5 mm jack. This is used as a headset (or earphone plus microphone) connector on mobile devices such as mobile phones and tablets and as a space-saving device on some computer sound cards, where many output channels are provided (e.g. for 7.1 analogue audio connections). Note that where such sockets are designed to accept 3-pole as well as 4-pole jacks, it is common practice for the signal earth to be carried on the 'ring 2' pole (the furthest ring from the 'tip' pole) rather than on the sleeve pole (for details see TRRS). However, check the card manufacturer's specifications. Another application of the 4-pole 3.5 mm jack is for 5.1 digital audio connections, where usually the tip carries the Front Left and Front Right signal, ring 1 carries the Rear Left and Rear Right signal and ring 2 carries the Centre and Sub-bass signal.
The 'B-type' ('B-gauge', or 'type B') jack has the same diameter sleeve as the A-type ones, but has a rounded and narrower tip and a narrower ring (it is generally available only as a 3-pole version). It is used almost exclusively in standard-sized patch bays, and is also known as a 'longframe jack' or as a 'Post Office jack', 'GPO jack' or 'phone jack' because of its original use in the manual switchboards of the British telephone network − however if the term 'phone jack' is used beware possible confusion with the 'phono' audio connector or with the modern style of telephone connectors (e.g. BT431a or RJ11), both of which are entirely different types of connector.
Some patch bays use a miniature version of the B-type jack, to enable more connectors to be accommodated per row. These have a sleeve diameter of 4.4 mm and are called Bantam jacks or TT (Tiny Telephone) jacks; both names are trademarked by Switchcraft.
Note that the ¼″ A-type and B-type connectors are not compatible. At the very least, connections between them would be unreliable, and there is a real danger of permanent damage being caused to the sockets if mating is attempted.
For information on the connections of all the 3-pole versions of jacks, see TRS.
[Note on history of usage: The term 'jack' historically relates to any mechanical device, especially one in which a lifting action is involved. In an electrical context, the term originally referred to a fixed female socket connector in which insertion of the plug operates one or more sets of make or break switching contacts (which may or may not be electrically independent of the connector contacts). Such switching contacts were originally required in the sockets of manual telephony switchboards, where the orientation of the sockets was usually such that the insertion of a plug operated the contacts via a lifting mechanism − hence the the adoption of the term 'jack' for these sockets. However, in time the term 'jack' was also applied to similar styles of socket, such as those used in PA applications, regardless of whether or not they incorporated switching contacts. The male plug which mates with these styles of socket was therefore referred to as a 'jack plug'. More recently, the word 'plug' was dropped (as superfluous) from that term. So, in modern usage, the term 'jack' may refer either to a female socket of any of the types described above (with or without switching contacts), or to its mating plug.]
There are no more definitions on this page. (The space below is to facilitate linking to the last few terms above.)
This page last updated 07-May-2017.