The company I work for has a pretty complex phone system.  Does a lot of customer service via phones.  Tracks time of calls and is also used to monitor phone conversations for quality control, and records caller # and id.  Always wondered what caller ID would show when a verification site would call.  No receptionist, only recorded message giving options to press keys for to go into a call waiting que.  HR has a direct line, and the rest of us have extensions.