Indirect ways of assessing past temperatures, using so-called temperature proxies, take measurements of responses to past temperature change that are preserved in natural archives such as ice, rocks and fossils.
Wikipedia has an article on: Reorder tone. Wikipedia. fast busy signal â(plural fast busy signals) (telephony) An audible signal on a voice phone line that sounds more frequently than a standard busy singal, indicating that no transmission path to the called phone number is available.
RE: regular busy vs fast busy. I always understood that a 'fast busy' indicated a busy from one central office switch to another central office switch. A slow busy indicates the person that you are trying to call is on the phone. A goggle search appears to agree for the most part.