Thanks for Aka and Richard first.

Actually, I was asked to develop an attendance system for pupils in a school. A few smartcard readers would be placed in the school main entrance. Each student has a smartcard. When one student arrives at the school, he/she needs to plug his smartcard into the reader. His/her card's ID will be checked at the database server. If his/her card is valid (not blacklisted), the time and his/her ID will be logged in the database and a LED and a buzzer sound will be on next to that reader.

These few smartcard readers and a PC-controlled clock will be connected to a single PC.

A few questions in my mind are:

1) Can I access each smartcard reader individually through the serial port or the RS422 bus (since I want to control the LED and the buzzer individually)?

2) How can I show the time on a LCD or LED array through the parallel port without an extra power supply for the display?


Hope someone can give me some hints.


--
Winson