How do I configure Apache2 to allow multiple simultaneous connections from same IP address?

By default, Apache2 seems to allow only 1 connection per IP address.

How do I configure Apache2 to allow multiple simultaneous connections from the same IP address?

Here is my situation:

1. a web app being hosted on a server.
2. a remote client makes an request that may take 15 seconds to complete.
3. the same remote client makes another (independent) request.
4. at present, the 2nd request sits in a queue until the 1st request completes, since Apache2 seems to impose a limit of 1 connection per IP address.

How do I override this default behaviour and allow the 2nd request to be processed in parallel?

thanks in advance, David Jones