Banana connector
Encyclopedia
Wire
A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads and to carry electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Standard sizes are determined by various...
(one conductor
Electrical conductor
In physics and electrical engineering, a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons...
) electrical connector
Electrical connector
An electrical connector is an electro-mechanical device for joining electrical circuits as an interface using a mechanical assembly. The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or...
used for joining wires to equipment. The term 4 mm connector is also used, especially in Europe, although not all banana connectors will mate with 4mm parts. The plugs are frequently used to terminate patch cords for electronic test equipment
Electronic test equipment
Electronic test equipment is used to create signals and capture responses from electronic Devices Under Test . In this way, the proper operation of the DUT can be proven or faults in the device can be traced and repaired...
. They are also often used as the plugs on the cables connecting the amplifier
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
to the loudspeaker
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
s in hi-fi
High fidelity
High fidelity—or hi-fi—reproduction is a term used by home stereo listeners and home audio enthusiasts to refer to high-quality reproduction of sound or images, to distinguish it from the poorer quality sound produced by inexpensive audio equipment...
sound system
Sound reinforcement system
A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience...
s.
The plug was invented in 1924 by Richard Hirschmann (former Richard Hirschmann GmbH & Co.).
Design
The plug consists of a cylindrical metal pin about 25 mm (one inch) long, with a diameterDiameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
of 4 mm, which can be inserted into a matching 4 mm socket to make an electrical contact. The pin has one or more lengthwise spring
Spring (device)
A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
s that bulge outwards slightly. These press against the sides of the socket, improving the electrical contact and preventing the pin from falling out. The curved profile of these springs is probably the origin of the name "banana plug". The other end of the plug has a lug connector to which a length of flexible insulated equipment wire can be attached, which is either screw
Screw
A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...
ed, solder
Solder
Solder is a fusible metal alloy used to join together metal workpieces and having a melting point below that of the workpiece.Soft solder is what is most often thought of when solder or soldering are mentioned and it typically has a melting range of . It is commonly used in electronics and...
ed, or crimp
Crimp connection
A crimp connection is achieved with a type of solderless electrical connector.Crimp connectors are typically used to terminate stranded wire. They fulfill numerous uses, including allowing the wires to be easily terminated to screw terminals, fast-on / quick-disconnect / spade-foot type terminals,...
ed into place. An insulating
Electrical insulation
thumb|250px|[[Coaxial Cable]] with dielectric insulator supporting a central coreThis article refers to electrical insulation. For insulation of heat, see Thermal insulation...
plastic cover is usually fitted over this rear end of the connector.
The rear end of a 4 mm plug often has a 4 mm hole drilled in it, either transversely or axially, or both, to accept the pin of another 4 mm plug. This type is called a "stackable" 4 mm plug.
For high voltage use, a special sheathed version of the banana plug and socket is used. This version has an insulating sheath around both the male and female connectors to avoid accidental contact. The sheathed male plug will not work with an unsheathed female socket, but an unsheathed male plug will fit a sheathed female socket.
Individual banana plugs and jacks are commonly color-coded red and black but are available in a wide variety of colors. Dual banana plugs are usually black with some physical feature such as a molded ridge marked "Gnd" indicating the relative polarity of the two plugs.
Besides plugging into specific banana jacks, banana plugs may plug into five-way or universal binding post
Binding post
A binding post is a connector commonly used on electronic test equipment to terminate a single wire or test lead. They are also found on loudspeakers and audio amplifiers as well as other electrical equipment....
s on audio equipment.
Derived plugs
A number of widely used plugs are based on combining 2 or more banana plugs with a plastic handle and other features for ease of use and to prevent accidental insertion in other such plugs. Many of these plugs are derived from the double banana plug consisting simply of two banana plugs spaced 3/4 inch (about 19mm) apart.US-style double banana (pictured): A plastic housing containing two banana plugs, allowing simultaneous connection of a signal line and a ground (earth) line; see the photo. The housing may allow the connection of individual wires, a permanently attached coaxial cable
Coaxial cable
Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
providing both signal and ground, or a coaxial connector such as the BNC connector
BNC connector
The BNC connector ' is a common type of RF connector used for coaxial cable. It is used with radio, television, and other radio-frequency electronic equipment, test instruments, video signals, and was once a popular computer network connector. BNC connectors are made to match the characteristic...
shown in the photo. By convention, multiple full-sized banana connectors are spaced on ¾ inch centers.
Older European audio equipment used double banana plugs with a 3rd center pin (round 4mm banana for speakers, 4 mm banana or flat pin for turntable to amplifier connection) for audio signals. The center pin prevents accidental insertion in mains sockets, except the Italian "type L" socket.
Some specialized multi-pin plugs and sockets consist of 5 or more banana plugs arranged in a circle.
Miniature banana connectors
A miniaturized version of the banana connector was also produced. About 1/3 the size of the standard connector, these were useful in high-density applications but never achieved the same sort of popularity as the larger banana connectors. They are substantially more fragile than the larger connectors. Multiple miniature banana connectors are usually spaced on ½ inch centers.Electrical safety
An exposed banana plug can obviously present electrical hazards if the wire to which it is attached is energized. A plug that is only partially inserted into a jack can also present a risk of accidental contact as the conductive surface of the plug will not be completely covered. The hazards include electric shockElectric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
, electrocution, burns
Burn (injury)
A burn is a type of injury to flesh caused by heat, electricity, chemicals, light, radiation or friction. Most burns affect only the skin . Rarely, deeper tissues, such as muscle, bone, and blood vessels can also be injured...
from accidental short circuit
Short circuit
A short circuit in an electrical circuit that allows a current to travel along an unintended path, often where essentially no electrical impedance is encountered....
s, and damage to the attached equipment.
Where electrical safety is an issue, various kinds of protected plugs and sockets are available. These have sliding covers on plugs and/or other devices to protect the user from accidental contact with live conductors, but are still largely compatible with the original design.
Voltmeter
A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to...
test leads
Test probe
A test probe is a physical device used to connect electronic test equipment to the device under test . They range from very simple, rugged devices to complex probes that are sophisticated, expensive, and fragile.- Voltage probes :Voltage probes are intended to measure voltages on the DUT...
and several other measurement and laboratory equipment. In this design, the metal banana plug is entirely sheathed in plastic and presses into a deep recess in the DVM. Alternatively, the DVM has the male part of the banana plug and it is deeply recessed; the test lead contains a sheathed banana jack.
In most European countries the standard mains power receptacle will physically accept banana and even US-style "double banana" plugs (the standard US pin spacing of 3/4 inch (19.05 mm) is close enough to the mains plug spacing of about 19 mm., and the pin diameter is also compatible), leading to a risk of electrical shock. For safety reasons, it can be difficult to purchase US-style laboratory "double banana" plugs in these countries.