Types of D-Sub Connectors
Depending on the device to be connected, the number of pins on a D-sub connector varies from 9 to 100, and these pins are arranged in two to five parallel rows. The pins are spaced out according to the connector’s density. Normal density has the widest space between the pins, followed by high-density and double-density D-sub connectors. Below are the D-sub types with their corresponding pin layouts and densities:[1]
| D-sub Type | Pin Layout | Density |
|---|---|---|
| DE-9 | 5–4 | Normal |
| DA-15 | 8–7 | Normal |
| DE-15 | 5–5–5 | High |
| DB-19 | 10–9 | Normal |
| DE-19 | 6–7–6 | Double |
| DB-25 | 13–12 | Normal |
| DA-26 | 9–9–8 | High |
| DA-31 | 10–11–10 | Double |
| DC-37 | 19–18 | Normal |
| DB-44 | 15–15–14 | High |
| DD-50 | 17–16–17 | Normal |
| DB-52 | 17–18–17 | Double |
| DC-62 | 21–21–20 | High |
| DD-78 | 20–19–20–19 | High |
| DC-79 | 26–27–26 | Double |
| DD-100 | 26–25–24–25 | Double |
| DF-104 | 21–21–21–21–20 | High |
Out of the many types of D-sub ports, only a few remain in use today in the computing world. DE-15 or DA-15 is the commonly used VGA connector for older monitors and computers, and DE-9 is a general-purpose D-sub port and was very common in older computers for I/O connections. Today, the VGA port has been replaced mainly by HDMI, Thunderbolt, and USB-C ports, while DE-9 has been succeeded by USB ports.
Although they are rarely used in computers and networking devices, D-sub ports are still widely used in many industrial devices, such as in the military, aerospace, medical diagnostics, and transportation.
Aside from their density types, D-sub connectors also fall into different categories:
- Combi D-Sub Connector – is a versatile type of D-sub that contains different connectors in a D-sub housing. This type of connector has a combination of contacts for signal, high current, high voltage, coaxial, or pneumatic.
- Dual-Port D-Sub Connector – consists of two 90-degree D-sub connectors stacked together. This type of D-sub connector is used mainly in applications where multiple connectors are required, but space is limited.
- Filtered D-Sub Connector – this type of D-sub is equipped with a filter for Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) for better signal quality.
- Standard D-Sub Connector – is high-quality and robust D-sub connector with different assembly parts for mounting and is designed for the most demanding applications.
D-Sub Ports: Pros and Cons
D-Sub connectors are designed to withstand harsh environments. The rugged connector has two screws on both sides that offer a semi-permanent, secure, and reliable connection. The wirings are covered with a sturdy plastic or rubber material. D-sub connections are usually left undisturbed once the screws are secured, resulting in a long-life cycle. D-sub hoods are also available if the connectors are exposed to extreme environments, although this is not necessary in most cases.
D-sub connectors have a respectable list of advantages. However, they also have several disadvantages. The most obvious disadvantage is their bulkiness. Portability is an important factor in modern devices, and there isn’t much room for connectors and ports as bulky as the D-sub. D-sub ports also lack a line for power; connected devices would usually require a separate power supply. However, its biggest drawback is the serial data transmission which is slower as compared to parallel transmission.
Serial Transmission vs. Parallel Transmission
Aside from size, speed is another determining factor that caused the D-sub port’s decline. Serial data transmission is at the core of D-sub ports, and it is considerably much slower than parallel data transmission. Serial connections use a single line to transmit data. Thus, data is transferred bit by bit. Conversely, the parallel transmission uses multiple I/O lines enabling it to transmit eight bits of data at a time. Therefore, parallel transmission transmits data at a higher speed than serial transmission, the reason why D-sub ports were gradually replaced by parallel connectors, such as USB cables. Due to multiple lines, however, parallel transmission creates more errors and noise than serial transmission. The signal quality deteriorates as data travels over longer distances. That’s why the serial connection is the more viable option for longer distances.
However, in computer connections, the distance between one device to another is relatively short. Parallel transmission can effectively transfer data at a much faster rate than serial transmission for such short distances. For example, you don’t need a lengthy cable to connect your monitor to your desktop. The parallel transmission that HDMI offers would be most ideal in such a setup: faster speed and more compact port.
Although parallel transmission has its disadvantages, its benefits surpass serial transmission, especially for devices that only need short connectors. Since speed and portability have become key characteristics of modern devices, such as laptops and desktops, D-sub ports gradually lost their shine to smaller and faster ports.
Conclusion
D-sub ports are now considered legacy ports used primarily in older monitors and computers. Some modern devices still include the traditional D-sub port for compatibility purposes. D-sub ports transmit data rather slowly, and they can no longer keep up with the demands of modern devices. Since portability is becoming a trend in modern devices, the bulky D-sub was eventually replaced by smaller and faster ports. Even though we don’t see D-sub ports in the consumer electronics scene today, they are still used in various industrial applications since they can withstand harsh environments and transmit signals over long distances with minimal errors and noise. We hope you found this article helpful. Check the other Linux Hint articles for more tips and information.
Sources:
[1] Computer Hope. D-sub Connector. https://www.computerhope.com/jargon/d/dbconnec.htm. August 02, 2020, Accessed February 22, 2022
