Mini-DIN connectors are 9.5 mm in diameter and come in seven patterns, with the number of pins from three to nine. Each pattern is keyed in such a way that a plug with one pattern cannot be mated with any socket of another pattern. An important aspect of why each of these 7 mini-DIN connectors are official standards is because they are each drastically different from the other, with no simultaneously and directly overlapping similarities in (1) pin arrangement.
(2) square key size and position.
(3) circular shielding metal skirt notches & metallic additions - unlike the nonstandard mini-DIN connectors which may have directly overlapping characteristics to each other or to the standard mini-DIN connectors.

The pin numbering for the plugs shown above is done left to right, bottom row to top row. Pin 1 will be on the lower left, and the highest pin number will be on the upper right.

WARNING:No references are cited for these pin arrangements. The mini-DIN 9-pin diagram is not the standard; the standard is nonuniform spacing on the first row and uniform spacing on the second. See, for example, a data sheet for mini-DIN 9 connector that shows a nonuniform spacing on the top row.

Non-standard connectors

Several non-standard sockets are designed to mate with standard mini-DIN plugs. These connectors provide extra conductors, and are used to save space by combining functions in one connector that would otherwise require two standard connectors.

Other non-standard connectors mate only with their matching connectors, and are mini-DIN connectors only in the sense of sharing the 9.5 mm plug body. These mini-DIN style plugs are not approved by the Deutsches Institut für Normung, the German standards body, and many applications could be considered proprietary.