There are a huge number of connectors for computer hardware.
Thankfully, those days are generally past, with USB being an open standard dominating the peripheral connectivity market.
Contents
9-Pin Dsub
One of the early connectors was the Serial port.
The D-subminiature connector standard had a broad range of connectors.
The DE-9 had nine pins arranged in two rows.
The D in the name comes from the D-shaped metal shield that runs around the connector pins.
It also provides some protection from electromagnetic interference.
The final part of the physical connector was a pair of optional screws on either end of the shield.
When the standard was published, however, D-sub connectors were amongst the smallest on the market.
Tip:You may have seen a similar connector on the back of some monitors.
The VGA monitor cable used a 15-pin D-sub connector DE-15, typically colored blue.
While superseded now by HDMI and DisplayPort, VGA was very popular for a long time.
Parallel vs.
Serial
Many of the connector standards at that time were parallel.
This meant t a large number of data pins that all transmitted data in sync.
This approach had two main issues.
First, you need many electrical pins to operate this way, making connectors large and unwieldy.
This essentially limits the maximum frequency at which you’re free to share data.
The only way to increase bandwidth further is to make connectors with even more data pins.
Its essential to ensure that there are two data connections, one for transmission in each direction.
Using a small number of connector pins allowed significantly smaller connector sizes.
This enables complete duplex transmission allowing bi-directional communication at full spec speeds.
Its use is easy now, but it can still be found in some use cases.
Networking hardware, mainly managed routers and switches, often offers a serial port as a local connectivity option.
Cables that have an ethernet port at one end are also available.
Devices are generally configured so that a DTE equipment needs to connect to DCE devices.
As such, the in and out pins are intentionally flipped on DCE vs. DTE devices.
Most modern devices contain an auto-detection feature, adapting to the use of either cable.
This was not a common feature in earlier implementations.
DTE devices are user devices such as a computer or managed online grid hardware.
DCE devices tend to connect to other communication media, like a modem.
Conclusion
The serial port is a computer connector port.
It uses a 9-pin D-sub connector known as DE-9.
In modern devices, it is essentially exclusively found on managed web link hardware.
The connector is visually similar to the VGA cable but has a lower pin count version.
