PS2 to USB Adapter: An Active Converter in a Small Shell
Quick answer / TL;DR: Short answer: buy an active PS/2-to-USB converter and match it to the device type – keyboard and mouse versions are usually not interchangeable. Expect six-key rollover at best, no hot-plug behaviour like native USB, and no support for exotic keys. For a single legacy keyboard in a lab, an active converter is reliable; for a fleet, replace the keyboards.
A patch cord is a stranded assembly: moulded boot, eight contacts, T568B.A PS/2 to USB adapter translates a serial keyboard or mouse protocol into USB. The two are not electrically compatible, so the adapter contains a microcontroller.
That is why a passive plug-shaped part costs a fraction of a working one and usually does not work.
What the Converter Does
| Layer | PS/2 | USB |
|---|
| Electrical | Open collector, 5 V | Differential serial |
| Protocol | Serial scan codes | Packet based |
| Hot plug | Not supported | Supported |
| Rollover | Limited | Up to NKRO |
The rollover limit is the practical difference for fast typists and for anyone using key combinations in CAD or trading software.
Selection Points
- Explicit keyboard or mouse labelling
- Stated support for multimedia keys
- External power for high-draw devices
- Metal shell rather than moulded plastic
A converter that draws power from the PS/2 port alone can brown out with an older keyboard that has LEDs and a backlight.
Real-World Applications
A laboratory keeping a specialised industrial keyboard alive uses one active converter per station. An office replacing ten standard keyboards should buy USB keyboards instead, because ten converters cost more than ten keyboards and add ten failure points.
Standards and Verification
| Reference | Relevance |
|---|
| USB-IF HID class | USB keyboard and mouse |
| IBM PS/2 technical reference | Legacy protocol |
| Local EMC rules | Converter compliance |
Compatibility with a specific legacy keyboard is not provided in the knowledge base. Test the actual device before buying in quantity.
Practical Notes
Keep one known-working converter as a reference. When a station fails, swapping in the reference part separates converter faults from keyboard faults in seconds.
Related reading: usb cable — blogs/news/usb-cable
Related reading: usb adapter — blogs/news/usb-adapter
Related reading: usb a to usb c adapter — blogs/news/usb-a-to-usb-c-adapter
Frequently Asked Questions
Why does a cheap adapter not work?
It is often passive and cannot translate the protocol.
Can one adapter do keyboard and mouse?
Some can, but most are type-specific.
Does it support NKRO?
No. Expect limited rollover.
Sourcing cables for a project, a store, or a private-label line? Contact our B2B sales team for specifications, certification evidence, and volume terms – FOB and CIF options available. Request a quote or sample.
