I'm making it up, but want to say it had a serial port. Also, fun fact - they emulated instead of redesigned literally for aesthetic reasons.
The article says it's because projectionists are familiar with the Palm Pilot UI (because to them it's just another tool), and rather than get them to re-learn a different UI, they used emulation to provide the same familiar UI on newer hardware.
We (technology/digital experts) take for granted our level of comfort in sussing out how a new UI works.