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.
6.3.4.1.2 Reorder tone is variously referred to as paths-busy tone, all-trunks-busy tone and fast busy tone. This signal is applied toward the caller when call blockage is encountered due to unavailability of equipment or channels. This signal shall be held applied as long as the caller remaions off-hook.