first and last pin. There are also two variations of the six-pin, seven-pin (one where the outer pins form 300° or 360° and one where they form 270°), and eight-pin (one where the outer pins form 270° and one where they form 262°) connectors. There is some limited compatibility; for example, a three-pin connector will fit any 180° five-pin socket, engaging three of the pins and leaving the other two unconnected; and a three-pin or 180° five-pin connector will also fit a 270° seven-pin or either eight-pin socket. In addition to these connectors, there are also connectors with 10, 12, and 14 pins. Some high-range equipment used seven-pin connectors where the outer two carried digital system data: if the connected equipment was incompatible, the outer two pins could be unscrewed from plugs so that they fitted into standard five-pin 180° sockets without data connections. As the keying is consistent across all connectors, it does not completely prevent incompatible connectors from mating, which can lead to damage; this is changed in Hosidentype, wrongly called Mini-DIN, which keys different connectors. Some "domino" five-pin connectors had a keyway on opposing sides of the socket, allowing it to be reversed. If used as a headphone connector, the plug sometimes had a cut-out in the body that, depending on which way the plug was inserted, would either allow (e.g.) external speakers to be switched off or not as required: inserting the plug one way would activate a switch on the periphery of the socket (thus switching off the speakers), whereas inserting the plug in the opposite orientation would not activate the switch (due to the cut-out in the plug body)—the left and right channels would not be transposed, as the plug was wired such that each headphone speaker was connected "top left–bottom right" and "top right–bottom left". Note that when rotating a DIN headphone connector 180 degress the polarity will be reversed. This generally doesn't affect the audio but if an adapter with a DIN headphone male connector and most other types of female headphone connector is used, the negative connection for both channels will be joined resulting in the audio being stereo with the DIN connector inserted one way and mono when inserted the other way. To avoid this and still be able to use a pair of headphones both with equipment that has a DIN headphone connector and also use it with other