Computer cabling and connectors

Computers connect to peripherals, networks and each other through a range of standardised cables and connectors, each defined by a pinout that states which conductor carries which signal. Getting the pinout right is essential, because a connector that looks identical may carry different signals on its pins depending on the standard, and a mismatch can prevent communication or, in some cases, damage equipment. Reference tables of pinouts are therefore a staple of computer cabling, covering ports for data, video and power.

Older serial and parallel ports illustrate the importance of wiring details. A standard serial cable connects matching pins straight through, but a null-modem cable deliberately crosses the transmit and receive lines (and certain handshake lines) so that two computers can talk directly to each other without a modem between them. Parallel printer cables and various device-specific leads each follow their own conventions, which is why labelled pinout diagrams are so useful when making or identifying a cable.

Modern computers rely heavily on the Universal Serial Bus (USB), a standardised connector and protocol that carries data and supplies power to a peripheral over the same cable, allowing devices to be connected and disconnected while the computer runs. USB replaced many earlier single-purpose ports with one flexible interface. Alongside such data links, structured cabling standards define how network and signal wiring is terminated and which pin maps to which conductor, so that components from different manufacturers work together predictably.

Frequently asked questions

What is a null-modem cable?

It is a serial cable with the transmit and receive lines crossed so that two computers can communicate directly with each other without a modem in between.

Why are pinout diagrams important?

Connectors that look alike can assign different signals to their pins, so a pinout diagram is needed to wire or identify a cable correctly and avoid faults.

What makes USB convenient?

USB carries both data and power over one standardised cable and allows devices to be plugged in or removed while the computer is running.