D-Type or D-Sub Connector

An overview, and information about the D-type (often called the D sub-miniature or D-sub) series of connectors widely used for multiway connections.

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The D-type range of connectors has been in widespread use for many years. They were first developed in 1952 by Cannon which is now part of ITT.

The D-type connector has been used in many applications as a multi-way connector, but it is probably most widely known as the connector used for RS-232 serial links. In fact the D-type connector was used for the serial link on most computers for many years, and today variations of D-type connectors are still found on most computers.

The D-type connector was originally termed a sub-miniature connector, and often today the connectors may be referred to as D sub-miniature connectors. Although these connectors were small when they were first introduced, the can no longer be thought of as true sub-miniature connectors.

Typical application for D-sub or d-type connector
D-sub connector on a module
Note the fixing that themselves have an internal thread so that the connector mating half can be secured to prevent accidental disconnection.

D-type connector basics

D-type connectors most commonly consist or two and sometimes more parallel rows of connections.

The connectors have a D-format metal shell. This not only provides mechanical strength to the connector, but it also provides some limited screening as well - the metal shells of the plug and socket make contact to provide screening. Also the panel mounting connectors are typically secured to the panel using nuts that have an additional thread that allows the mating connector to be secured to it to prevent it working loose.

Additionally the free connectors can have back-shells that can provide screening and can be connected to the cable screen, or if plastic, they can provide protection. Strain relief on the cable is also provided.

D-type or D-Sub connector on a computer video screen lead.
D-type or D-Sub connector on a computer video screen lead.

As would be expected, the connector containing the pins is the male D-type connector, whereas the connector containing the receptacle pins is the female.

The original D-type connectors had two rows on pins - the overall number of pins was an odd number and this resulted in the connector having one more pin in one row that the other, giving rise both e D shape which also prevented mating of connectors wit the incorrect orientation.

Pin arrangement for a d-sub / d-type connector DE-09
Pin arrangement for a d-sub / d-type connector DE-09

D-type connector numbering

The original numbering system for the D-type or D-sub connector used D as the prefix (giving its name to the series) and this is followed by A, B, C, D, or E depending upon the shell size. This is followed by a number which indicated the number of pins. A final letter is a P or S indicating whether the connector is a plug or socket respectively.

Examples of connector numbering might be DB-25P for a 25 pin D-type plug or DE-9S for a 9 pin socket.

This original series of D-type connectors had pin numbers of 9, 15, 25, 37 and 50 pins and also a 19 way is available. The common pin configurations are: A=15 pin, B=25 pin, C=37 pin, D=50 pin, E=9 pin.

The pins in the more common connector types with two rows of pins (e.g. 9, 15, 25 and 37 way) are spaced approximately 0.108 inch (2.74 mm) apart with the rows spaced 0.112 inch (2.84 mm) apart.

High pin counts and higher pin densities can be achieved using more rows of pins.

D-Sub Connector Normal Density
Name Pin layout
DA-15 8 - 7
DB-25 13 - 12
DC-37 19 - 18
DD-50 17 - 16 - 17
DE-09 5 - 4
DB-19 10 - 9

Beware the confusion by some suppliers / manufacturers selling the connectors under incorrect type designations. Sometimes connectors that should be designated as DE-09 are sold as DB-09. DB-9 nearly always refers to a 9-pin connector with an E size shell. 

D-Sub Connector High Density
Name Pin layout
DA-26 9 - 9 - 8
DB-44 15 - 15 - 14
DC-62 21 - 21 - 20
DD-78 20 - 19 - 20 - 19
DE-15 5 - 5 - 5
DF-104 21 - 21 - 21 - 21 - 20

Sometimes the High Density D-type connectors may also be referred to in non-standard ways, for example DB-15HD or even DB-15 or HD-15, and similarly for other D-type high density connectors.

D-Sub Connector Double Density
Name Pin layout
DA-31 10 - 11 - 10
DB-52 17 - 18 - 17
DC-79 26 - 27 - 26
DD-100 26 - 25 - 24 - 25
DE-19 6 - 7 - 6

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