Device Access/Lock for Users in Windows - How does it work? Is it configurable?

Question

Explanation:

An application that I use will listen on a serial port and uses a video capture card. If I leave that application open and switch users to start the application again, that other user won't have access to the serial port and video capture card. It seems to be blocked by the first, still logged in user.

This implies to me that the operating system will limit the access to certain devices* to the first users that use the device.

*When saying devices I mean hardware devices as shown in the device manager, i.e. comport cards, video capture cards, etc..

Questions:

• Where does this limitation exist? Is it on Windows(kernel?)-level or on application level?
• How does this device access control work in Windows if it is implemented by the OS?
• Where can I read up on it?
• Can I disable it altogether?
• Can I, as a local administrator, take control of a device from a user without killing the application that uses it?

Boundaries:

I know it would be easiest to make sure the application is not open twice. Still, it would be useful to me to have a deeper understanding on why the device can't be used by both instances or alternatively if I can make a second instance take away the devices from the first.