A banana connector is a single-wire (one conductor) electrical connector used for joining wires to equipment. The term 4 mm connector is also used, especially in Europe,because the pin’s diameter is nominally 4 millimetres (0.16 in).The pin has one or more lengthwise springs that bulge outwards slightly, giving the appearance of a banana.
The original plug consists of a cylindrical metal pin about 20 millimetres (0.79 in) long.However other sizes have emerged, such as 15 millimetres (0.59 in) pins, which can commonly be found in the US. Banana plugs and cables are typically rated for 30 V at 15 A, but there are versins rated up to 30A. Typical applications are test cables on electronics laboratories and speaker connections on HiFi systems.
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.
A typical design is now required (IEC 61010) on digital voltmetertest leads 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. The sheathed male plug will not work with an unsheathed female socket, but an unsheathed male plug will fit a sheathed female socket.This kind of sheathed banana connectors are typally used up to 1000V voltages.
Last but not least: Screw locking Banana.The UHF connectoris a threaded RF connector design RF connector useable up to 100 MHz (typically used for HF and lower VHF frequencies). Thsi connector has approximately 0.156 inch (4mm) diameter pin and socket for the inner conductor. It is possible to mate UHF connector female with banana plug.