The DIN connector is an electrical connector that was standardized by the (DIN), the German Institute for Standards, in the early 1970s, although it was already in use by the mid 1960's. The male DIN connectors (plugs) feature a 13.2 mm diameter metal shield with a notch that limits the orientation in which plug and socket can mate. The range of DIN connectors, different only in the configuration of the pins, have been standardized as DIN 41524 / IEC/DIN EN 60130-9 (3-pin at 90° and 5-pin at 45°); DIN 45322 (5-pin and 6-pin at 60°); DIN 45329 / IEC/DIN EN 60130–9 (7-pin at 45°); and DIN 45326 / IEC/DIN EN 60130-9 (8-pin at 45°). In consumer electronics, the term "DIN connector" identifies types of cylindrical connectors that the German Institute for Standards (DIN) had initially standardised for analog audio signals. Some DIN connectors have been used in analog video applications, for power connections, and for digital interfaces, such as the MIDI (DIN 41524), the IBM PC keyboard and the IBM AT keyboard connectors (DIN 41524). The original, technical standards for these models of DIN connector are unavailable, and were replaced with equivalent connectors, such as the international standard IEC 60130-9. Standards The term "DIN connector" alone does not unambiguously identify any particular type of connector unless the document number of the relevant DIN standard is added (e.g., "DIN 45322 connector"). Some DIN connector standards are: DIN 41524, for circular connectors often used for audio signals or some digital signals like MIDI DIN 41612, rectangular connectors used to connect plug-in cards to a back plane or motherboard DIN 41652 D-subminiature connectors used for computer data and video DIN 41585 automotive coaxial connectors Circular connectors The plugs consist of a circular shielding metal skirt protecting a number of straight round pins. The pins are 1.45 mm in diameter and equally spaced (at 90°, 72°, 60° or 45° angles) in a 7.0 mm diameter circle. The skirt is keyed to ensure that the plug is inserted with the correct orientation, and to prevent damage to the pins. The basic design also ensures that the shielding is connected between socket and plug prior to any signal path connection being made. There are seven common patterns, with any number of pins from three to eight. Three different five-pin connectors exist, known as 180°, 240°, and domino/360°/270° after the angle of the arc swept between the