The HP 300LX was one of the first handheld PCs designed to run the Windows CE 1.0 operating system from Microsoft.

The device also sported a full PC card slot, a serial link cable plug, and an infrared port.

On the back of the device is the proprietary serial connection which has a maximum baud rate of 115,200 bit/s and the power adapter port.

A single mono speaker, ROM door and battery compartment are located on the underside of the device.

They consisted of essentially the same hardware, but were shipped with a cable and software combo that allowed for using select Ericsson phones as modems.