Got it. Seems this is an idea solution then: Source: http://www.adafruit.com/product/1712

Thank you for your reply.

• 1. How about connecting a speaker to the USB Audio Adapter then?
  2. What about connecting a 50 Ohm speaker like:

http://www.visaton.com/en/industrie/klein/k40_50.html

to the Pi?

We are in the process of developing a carpark controller which are located next to the actual barrier. We wish to include an Intercom which allows communication to the management office. To add a microphone seems next to impossible unless one uses a USB Audio Adapter like this one: 1475-00.jpg As fo...