I have an old style PS1 machine with the digital controllers. Can I just plug in the dual joystick controllers? Do they work with the original PS machines?
Yes. The Dual Shock controllers should work with any PSX, PSOne, or PS2, but the games need to be designed to work with them. Pretty much all PS2 games work with them, but not all PSX games work with them because the Dual Shock PSX (which was a PSX with a Dual Shock controller, nothing special about the actual console) came out after the PSX had been out for a while.