The name on the caller ID says Netprowa. Just loud beeps more like some one is dialing numbers then a fax machine sound. http://www.netprowa.com/ is the site I found from google, sounds like a scam they want you to enter your phone number to remove you from their list.. I just think its a way to obtain more numbers. If you don't answer they call you back right away.
Netprowa calls multiple times daily, always a fax machine sound, calls at all times starting before 7am. Several numbers on caller id 720-606-7092, 720-606-7084, 720-606-7101....call them and return the favor at 720-398-0269