Question 1

What is the difference between a serial cable and a USB-to-serial adapter?

Accepted Answer

A serial cable is a passive lead connecting two devices that both have physical serial (RS232) ports, while a USB-to-serial adapter contains an active conversion chip that creates a virtual COM port on a USB-equipped computer. If your PC or laptop has no DB9 port — which is the case for virtually all modern machines — you need an adapter, not a straight cable. The two are not interchangeable.

Question 2

Is an FTDI chipset really worth the extra cost over a cheap CH340 adapter?

Accepted Answer

Yes, for anything beyond casual one-off use. FTDI chips have native driver support baked into Windows 10/11, macOS, and Linux kernels, meaning they work reliably across OS updates without driver conflicts. CH340 and some Prolific PL2303 adapters have a history of breaking after Windows updates or refusing to install cleanly on macOS. The price difference between a budget CH340 cable and a proper FTDI adapter is typically modest — well within the 12 £ to 16 £ range — and the reliability gain is significant.

Question 3

What does COM port retention actually do, and do I need it?

Accepted Answer

COM port retention ensures that Windows assigns the same COM port number to your adapter every time you plug it in. Without it, Windows may assign COM3 one session and COM7 the next, which breaks any software configured to communicate on a specific port. You need it if you use terminal emulators, PLC programming software, or any industrial application that references a fixed COM port. For a one-time configuration task, it's less critical.

Question 4

Can I use an RS232 serial cable with RS485 equipment?

Accepted Answer

No — RS232 and RS485 are electrically incompatible standards and cannot be used interchangeably. RS232 is a point-to-point standard with voltage levels between ±3V and ±15V, while RS485 uses differential signalling and supports multi-drop networks over much longer distances. Using the wrong cable will result in no communication at best, and potential damage to equipment at worst. If your device specifies RS485, you need a dedicated RS422/RS485 adapter such as the Equip USB-A to RS-422/485 in this catalogue.

Question 5

What serial cable pitfalls should I avoid when buying online?

Accepted Answer

The biggest trap is buying a cheap USB-to-serial adapter without checking the chipset — many budget listings don't disclose whether they use FTDI, CH340, or a counterfeit chip, and counterfeit FTDI chips are a known problem on certain marketplaces. Stick to named brands (StarTech.com, Lindy, Digitus) that explicitly state FTDI in the product description. A second pitfall: confusing straight-through and null modem wiring. Connecting two PCs directly requires a null modem cable; connecting a PC to a peripheral (router, switch, PLC) typically requires a straight-through cable. Getting this wrong means no communication, and it's an easy mistake to make.

Question 6

How long can an RS232 serial cable be before signal quality degrades?

Accepted Answer

The RS232 standard specifies a maximum of 15 metres (roughly 50 feet), though in practice reliable communication is possible at longer distances with low baud rates and quality shielded cable. At 9,600 baud with a well-shielded cable, runs of 30–50 metres are achievable in clean environments. In electrically noisy settings — factories, server rooms with heavy switching equipment — keep runs short or switch to RS485, which supports distances up to 1,200 metres by design.

Question 7

Are serial cables still relevant in 2026?

Accepted Answer

Absolutely — serial interfaces remain the standard for configuring network equipment (routers, managed switches, firewalls all have console ports), programming industrial PLCs and controllers, and connecting barcode scanners and label printers in warehouse environments. The RS232 port may have vanished from consumer laptops, but the protocol itself is very much alive in professional and industrial settings. The demand for USB-to-serial adapters has actually grown as modern PCs dropped physical COM ports while legacy equipment remained in service.

Serial Cables Price Comparison

Digitus Datatransfer extension cable, D-Sub9/M - D-Sub9/F

Digitus Datatransfer extension cable, D-Sub9/M - D-Sub9/F

Digitus Datatransfer connection cable, D-Sub9/F - D-Sub9/F

Digitus Datatransfer connection cable, D-Sub9/M - D-Sub9/M

Digitus Zero-Modem Connection Cable

Digitus Datatransfer extension cable, D-Sub9/M - D-Sub9/F

Microconnect SCSENN2N serial cable White 1.8 m DB9

Digitus Datatransfer extension cable, D-Sub25/M - D-Sub25/F

LogiLink AU0031 serial cable Black USB Type-A DB-9

ROLINE RS232 Cable, DB9 M - F 3 m

ROLINE RS232 Cable, DB9 F - F 1.8 m

Datalogic 90A052138 serial cable Black 4.5 m RS-232

Motorola CBL-58918-03 serial cable Black 0.8 m RS232 DB9

Manhattan USB-A to Serial Converter cable, 1.8m, Male to Male, Serial/RS232/COM/DB9, Prolific PL-2303RA Chip, Black/Silver cable, Three Years Warranty, Polybag

Manhattan USB-A to Serial Converter cable, 45cm, Male to Male, Serial/RS232/COM/DB9, Prolific PL-2303HXD Chip, Black/Silver cable, Three Year Warranty, Polybag

Manhattan USB-A to Serial Converter cable, 45cm, Male to Male, Serial/RS232/COM/DB9, FTDI FT232RL Chip, Equivalent to ICUSB2321F, Black/Silver cable, Three Years Warranty, Polybag

Zebra CBA-R71-C09ZAR serial cable Black 2.8 m RS232 DB9

Cisco CAB-ASYNC-8= serial cable Green 3 m

Cablenet 2m USB 2.0 Serial DB9/25 Converter

Microconnect USB3.1CRS232 serial cable Black 1 m USB C DB9

Vivolink VLCPARS232/25M serial cable Black RS-232

Vivolink PRORS3 serial cable Black 3 m D-sub 9 pin

Vivolink PRORS1 serial cable Black 1 m D-sub 9 pin

Vivolink PRORS2.0 serial cable Black 2 m D-sub 9 pin

Serial Cables Price Comparison