page_title: Banana connector
section_title: Electrical safety
hierarchical_section_title: Banana connector / Electrical safety
caption_attribution_description: English: Two programmable power supplies by Hameg Zwei programmierbare Labornetzteile von Hameg
context_page_description: A banana connector is a single-wire electrical connector 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 4 mm parts, and 2 mm banana connectors exist. Various styles of banana plug contacts exist, all based on the concept of spring metal applying outward force into the unsprung cylindrical jack to produce a snug fit with good electrical conductivity. Common types include: a solid pin split lengthwise and splayed slightly, a tip of four leaf springs, a cylinder with a single leaf spring on one side, a bundle of stiff wire, a central pin surrounded by a multiple-slit cylinder with a central bulge, or simple sheet spring metal rolled into a nearly complete cylinder. The plugs are frequently used to terminate patch cords for electronic test equipment, while sheathed banana plugs are common on multimeter probe leads.
context_section_description: Quality banana plugs and cables are typically rated for 30 V at 15 A. Cheap versions can have worse insulation, and might not withstand 15 A at all. Unsheathed banana connectors are not usually rated for mains voltage.
  One reason why banana connectors are not rated for mains usage is that an exposed banana plug or socket can present a shock hazard if connected to an energized source. A plug that is only partially inserted into a jack can also present a risk of accidental contact, because the conductive surface of the plug will not be completely covered. This can especially happen if a 20 mm long plug is inserted into a socket that is only intended for 15 mm long plugs. Some banana plugs have exposed set screws that are electrically connected to the wire. When stacking plugs using transverse holes in a plug, large parts of the pin of the second plug are exposed.  Another reason why banana connectors are not rated for mains usage is the lack of double insulation of wires and connectors. The hazards include electric shock, electrocution, burns from accidental short circuits, and damage to the attached equipment. 
  Where electrical safety is an issue, sheathed plugs and sockets are used. These plugs have fixed or sliding sheaths or other devices to protect the user from accidental contact with live conductors, but are still largely compatible with the original design. When inserted, the sheaths of the plug and socket overlap fully, ensuring that no live metal is exposed. A typical design is now required (IEC 61010) on multimeter test leads and several other measurement and laboratory equipment. In this design, the metal banana plug is entirely sheathed in a plastic tube and inserts into a deeply recessed jack in the multimeter. Alternatively, the equipment may use a deeply recessed male banana plug, while the test lead uses a sheathed banana jack. Additionally, the test lead wire must be made with insulation rated for higher voltages.
  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.
caption: Two Hameg programmable power supplies, top supply has screw-type banana jacks, bottom supply has safety-type banana jacks
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