Serial cables

Serial cables connect PCs, routers, modems, industrial controllers, label printers and test equipment over RS-232 and related serial interfaces. Our range covers connection cables, extension leads and adapter cables, with Delock, InLine, EXSYS and StarTech.com among the main brands.

How to choose a serial cable

Connector type and gender. Check whether each end needs a 9-pin D-sub (DB9), a 25-pin D-sub, an RJ45 plug or a USB connector, and whether it must be male or female. Most mistakes happen here, so look at the ports on both devices before ordering.

Straight-through or null modem. A straight-through cable links a computer to a device such as a modem, while a null modem cable has crossed transmit and receive lines for linking two computers or two terminals directly. If a connection shows no data, the wrong wiring is a common cause.

Interface standard. Most serial cables carry RS-232, but industrial equipment often uses RS-422 or RS-485, which have different wiring and suit longer runs. Read the device manual and match the standard, not just the plug shape.

Length and shielding. RS-232 loses reliability as cables get longer, especially at higher baud rates, so buy the shortest length that reaches. In workshops or near motors and power cabling, choose a shielded cable to limit interference.

USB adapters and drivers. If the computer has no serial port, a USB to serial adapter cable is the usual solution. Check that it supports your operating system and that the chipset is recognised by the equipment's configuration software.

Serial cable brands we carry

• Delock: a German-based supplier with a very large catalogue of cables, adapters and interface products, which is why it makes up the biggest share of this category.
• InLine: a German brand offering computer cables and connectivity accessories in many lengths and connector combinations.
• EXSYS: specialises in serial and I/O interface products such as serial cards and USB to serial adapters, which suits industrial and laboratory use.
• StarTech.com: a connectivity brand known for IT-focused adapters, including USB to serial products used by network and support engineers.
• Digitus: a brand from ASSMANN Electronic covering cabling and network connectivity, with a focus on structured installations.
• LINDY: a connectivity specialist known for cables, KVM and audio-video accessories sold to professional users.

Also in our range: ACT, Shiverpeaks, ROLINE, S CONN MAXIMUM CONNECTIVITY, EFB-Elektronik and Renkforce.

Serial cable FAQ

What is a serial cable used for?

A serial cable transfers data one bit at a time between two devices. It is still widely used to configure switches and routers through a console port, to control industrial machines and to connect older peripherals such as scanners, card readers and measuring instruments.

Do I need a null modem or a straight-through cable?

Use a straight-through cable when connecting a computer to a device that acts as data equipment, such as a modem. Use a null modem cable when joining two computers or two similar devices directly. The device manual normally states which one applies.

Can I use a serial cable if my computer has no serial port?

Yes, with a USB to serial adapter cable. It adds a virtual COM port to the computer and works with most serial equipment. Check driver support for your operating system before buying, particularly for older software.

How long can an RS-232 serial cable be?

The RS-232 standard is generally quoted at about 15 metres, but usable length depends on baud rate and cable quality. Lower speeds and shielded cable allow longer runs. For distances well beyond that, RS-422 or RS-485 equipment is usually the better choice.