How do I send control signals without using the parallel port?

I'm working on a project to control a switch from a vb.net application. The switch fires when one terminal is at 0V for about 1/2 sec. I've got this working with the parallel port, by setting one of the pins to 0V to trigger the switch. However, for various reasons, I now need another solution. I've been looking at the serial port, but it changes too fast. Any ideas? Thanks!!!!
How do I send control signals without using the parallel port?
There are myriads of Digital Output cards you could plug into your PC. Using the parallel port is not a good idea as there is no electronic isolation between the PC and whatever you are switching. Ensure you buy a card which comes with software and examples. Some are very cheap others not so. Just search for 'Digital Output cards' in your favourite search engine.

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