Why D-Sub Connectors Remain Relevant: Types and Applications Explained

Since D-SUB connector (D-subminiature connector) was created in the 1950s, it still plays a key role in many fields such as industrial control, communication interface, medical equipment and so on, due to its robust structure, multi-pin options and wide compatibility.This article will help you learn more about the types of D-SUB connectors, the number of pins, and their specific application scenarios, answer the question of why it is still relevant in the modern era, and help electronics engineers, purchasers, OEMs, and DIY enthusiasts make informed decisions.

 

1.What is a D-SUB connector？

The D-SUB connector (D-subminiature connector) is a multi-pin electronic connector which is characterized by a D-shaped metal housing that ensures proper mating of the plug to the socket.It is usually divided into two forms: male plug and female socket.

D-SUB was originally used for the serial interface connection of computers and communication devices, such as the RS-232 serial interface, but is still used today in a variety of industrial applications due to its excellent immunity to interference and mechanical stability.

 

2.Main types of D-Sub connectors

D-Sub connectors can be subdivided into the following categories based on pin density, internal layout and functionality expansion:

2.1. Common Density

These are the most classic models and the most widely used.

Model	Number of Pins	Common Applications
DE-9（DB9）	9	Serial interface communication (RS-232), PLC, embedded debugging port
DB-15	15	VGA interface, industrial monitor
DB-25	25	Parallel printer, I/O expansion
DB-37/50	37 / 50	Multi-channel control, measurement systems, analog signal acquisition

Explore full range of standard D-sub connectors

2.2. High-Density models

The three-row pin layout accommodates more channels in the same size housing for volume-sensitive devices.

Model	Number of pins	Application
HD-15	15	Analog video transmission (e.g., VGA), aerial image transmission module
HD-26/44/62/78	26~78	Data centers, embedded control boards, test equipment

Example Product:Left Right Angled Hd15 Male To Straight Hd15 Male

2.3. Mixed Layout

Integration of different types of pins (e.g. signal, power, coaxial, HF) in the same interface for highly integrated systems.

Application Scenarios	Recommended model
Robot control	DB13W3 (3 power + 10 signal)
Medical Imaging	DB9+Fiber Optic Hybrid
Flight control system	Customized DB series to support reinforcement and filtering

Example Product: Mixed Layout D-sub 7W2 Connector

2.4. Filtered D-Sub

Built-in electromagnetic interference filtering components, effectively shielding high-frequency noise, suitable for equipment with high signal integrity requirements.
a.Commonly used in：medical equipment, industrial buses, military systems
b.EMI suppression in the frequency range of 50MHz~1GHz or more
2.5. Waterproof D-Sub

With IP67/IP68 protection rating, it is suitable for outdoor and harsh environments:

Application	Feature
On-board diagnostic interface	DE-9 Waterproof housing，Oil and vibration resistant
Industrial Outdoor Boxes	DB-15 With sealing ring and thread locking

2.6. MIL-SPEC D-Sub

D-Sub that meets the requirements of high stability and high environmental adaptability in the military or aerospace field.
Standards: MIL-DTL-24308,etc.
Features：high metal density housing, metal locking, corrosion resistance, wide temperature range (-55~125°C)

3.Various models of D-SUB connector application scenarios in detail

3.1. DB9

Typical Applications：

• Serial Communication - especially the RS-232 protocol connection.
• CNC machinery and equipment, embedded systems
• Old modem, POS, PLC programming interface

Advantages：

• Simple and easy to use
• Widely supported communication protocols

Example Product: USB to DB9 Female Right-Angle RS-422/485 Converter Cable

3.2 DB15

Typical applications：

• VGA port：for image signal transmission from computer monitor to host computer
• Game controller ports (e.g. old-style joystick ports)
• Control signal transmission in audio/video equipment (some specialized equipment)

Advantages：

• Supports high-frequency signals
• Stable analog video transmission

Example Product：VGA Right Angle, 90° DB15 Male to Male

3.3 DB25

Typical applications：

• Parallel Printer Port
• Multiple RS-232 serial communications
• Analog signal control port for audio/broadcast equipment
• Instrumentation Data Transfer Interface

Advantages：

• Supports synchronized transmission of multiple signals
• Multiple pins for complex control logic

Example Product：USB 3.1 Type-C to DB25, Parallel Printer Cable

3.4 DB37

Typical Applications:

• Industrial Automation: Multi-Channel Data Acquisition and Sensor Control
• Military equipment and specialized test instruments

Advantages：

• A large number of I/O signal interfaces
• High anti-interference capability

Example Product：DB37 Female to Female, Serial Cable

3.5 DB50

Typical Applications:

• Network communication interfaces (e.g., some older network routers)
• Data transmission ports for aerospace equipment
• Rack-mounted control system

Advantages：

• Supports large-scale data transfer
• High-density design saves space

Example Product: DB50 Female to DB50 Male

 

4.Why Do D‑SUB Connectors Stand the Test of Time?

Despite the availability of more modern connectivity standards such as USB, HDMI, etc., D-SUB connectors are still widely used for a number of reasons:

• Durability: The metal housing has good mechanical protection and electromagnetic shielding capability.
• Versatility：Supports multiple types of transmission from signal, data, control, and power.
• Industrial Compatibility：Supports multiple types of transmission from signal, data, control, and power.
• Maintainability：Simple structure for easy maintenance and replacement.
• Cost-effective：Most D-SUB components are relatively inexpensive and low maintenance.

5.How to Choose D-SUB by Application

To make it easy for selection, we divide the common application scenarios into five categories: industrial automation, communication equipment, consumer electronics, automotive electronics and military/aerospace, and list the recommended D-SUB models and selection points.

5.1. Industrial Automation

Typical equipment：PLC controllers, sensor modules, industrial control cabinets

Recommended models：DB9、DB15、DB25

Selection points：

• Choose the anti-interference model with metal housing to enhance the ability of electromagnetic interference (EMI) resistance.
• Pick the number of pins according to the signal type and the number of control channels, DB25 is suitable for multi-channel IO communication.
• It is recommended to choose the one with fixing screw design to prevent the vibration from loosening.

5.2. Communication & Networking

Typical devices：Typical devices: modems, routers, serial servers, Controller Area Network

Recommended models：DB9, DB15 (serial port), DB25 (parallel port)

Selection points:

• For RS-232, RS-485, RS-422 communication, usually use DB9 serial connector
• Optional solder-type, crimp-type, or shielded connectors, depending on the installation method.
• Shielded interfaces are recommended for network communications to prevent data interference.

5.3. Consumer & Multimedia

Typical devices：old joysticks, projectors, VGA monitors, printers

Recommended models：DB15（VGA）、DB25（print parallel port）

Selection points：

• VGA video transmission preferred DB15 high density connector (HD15)
• If used for printing devices, check whether parallel interface communication is supported.
• Note compatibility with converters (e.g. USB to VGA, USB to parallel port)

5.4. Automotive Electronics

Typical devices：OBD diagnostic equipment, car data logger

Recommended model：DB9 (for RS-232 diagnostic interface)

Selection points:

• Mostly serial communication, need to confirm support for RS-232 or CAN bus standard
• Need to have high temperature resistance, anti-vibration performance, may select industrial-grade models

5.5. Aerospace & Defense

Typical devices：flight control system, radar interface, weapons control unit

Recommended models：DB15、DB25、DB37、DB50

Selection points：

• Choose MIL-DTL-24308 Military Specification D-SUB Connector
• Requires extremely high reliability, waterproof/corrosion-resistant design
• Metal housing, gold-plated contacts recommended for extreme environments

 

6.How to buy the right D-SUB connector?

You can refer to the following aspects when selecting a model:

Usage：Is it used for serial communications, video signals, control signals, etc.?

Number of pins and density：is space limited? How many signals are needed?

Housing material：Is waterproof and dustproof (optional IP67 protection level) required?

Installation：Does it support panel fixing, screw locking, etc.?

Cable type：compatible cable types, lengths, and shielding requirements

Quick Reference Table：

Application Scenario	Recommended Models	Communication Type
Industrial Control	DB9/DB25	Serial / Parallel
Communication Equipment	DB9/DB15/DB25	Serial / Parallel
Multimedia Devices	DB15/DB25	Analog Video
Automotive Electronics	DB9	Serial
MIL-spec / Aerospace	DB15~DB50	Serial / Parallel

 

7.FAQ:Frequently asked questions

Q1: Are D-SUB and DB9 the same thing?

A：D-SUB is a general term for connectors, and DB9 is one of the standard 9-pin models.Commonly used models are DB15, DB25 and so on.

Q2: Can the DB9 interface be used on modern computers？

A：While most modern PCs no longer come with a DB9 serial port, compatibility can be achieved with a USB to DB9 adapter.

Q3: Can D-SUB connectors be used for video transmission?

A：Yes, for example VGA (Video Graphics Array) is a D-SUB based 15-pin connector for analog video signal transmission.

Q4: How can I tell which D-SUB model I need?

A：Judgment is based on the number of pins required, type of data transfer (serial/parallel), space constraints, and application equipment.Refer to the pin count and application comparison table.

Q5: Will D-SUB be obsolete?

A：Although new interfaces continue to emerge, D-SUB is still irreplaceable in industrial, military and aerospace fields due to its solid, reliable and easy-to-maintain characteristics.

 

Although D-SUB connectors were introduced in the last century, their stability, versatility, and low cost still make them indispensable in today‘’s industrial and communication systems.From small DB9 serial communications to large DB50 industrial control interfaces, the D-SUB series continues to provide reliable support for engineering applications worldwide.