circuit and ports

[shamil]

I have a circuit which detects motion in a room. I use relay in this circuit. I want to detect with program in computer if relay switches. I think i have to work with ports but don't know how to send signal to port that i can detect that signal from my program. What is the easy and useful way to do this?

[Tomi Engdahl]

Read some ideas here
http://www.epanorama.net/circuits/paral ... html#input

Other ports that can be quite easily used for interfacing applications to get signal to PC are joystick interface (button inputs) and RS-232 port (modem status signal / handshakign inputs).