A hotline is a point-to-point communications link in which a call is automatically directed to the preselected destination without any additional action by the user when the end instrument goes off-hook. An example would be a phone that automatically connects to emergency services on picking up the receiver. Therefore, dedicated hotline phones don't need a rotary dial or keypad. There are also hotlines between states with nuclear weapons, like the Moscow–Washington hotline. A hotline can also be called an automatic signaling, ringdown, or off-hook service.
Hotlines for crisis and service 
True hotlines cannot be used to originate calls other than to preselected destinations. However, in common or colloquial usage, a "hotline" often refers to a call center reachable by dialing a standard telephone number, or sometimes the phone numbers themselves.
This is especially the case with 24-hour, noncommercial numbers, such as police tip hotlines or suicide crisis hotlines, which are manned around the clock and thereby give the appearance of real hotlines. Increasingly, however, the term is found being applied to any customer service telephone number.
Hotlines between states 
The most famous hotline between states is the Moscow–Washington hotline, which is also known as the "red telephone". This direct communications link was established on June 20, 1963, in the wake of the Cuban Missile Crisis.
Already during World War II, two decades before the hotline Washington-Moscow was established, there was a hotline between the Cabinet War Room bunker under Downing Street and the White House in Washington. From 1943–1946 this link was made secure by using the very first voice encryption machine, called SIGSALY.
A hotline connection between Moscow and Bejing was used during the 1969 frontier confrontation between the two countries. The Chinese however refused the Russian peace attempts and ended the communications link. After a reconciliation between the former enemies, the hotline between China and Russia was revived in 1996.
On his visit to the Soviet Union in 1966, French President Charles de Gaulle announced that a hotline would be established between Paris and Moscow. The line was upgraded from a telex to a high-speed fax machine in 1989.
A London-Moscow hotline was not formally established until a treaty of friendship between the two countries in 1992. An upgrade was announced when Foreign Secretary William Hague visited Moscow in 2011.
On June 20, 2004, both India and Pakistan agreed to extend a nuclear testing ban and to set up a hotline between their foreign secretaries aimed at preventing misunderstandings that might lead to nuclear war. The hotline was set up with the assistance of United States military officers.
India and China announced a hotline for the foreign ministers of both countries while reiterating their commitment to strengthening ties and building "mutual political trust".
North and South Korea 
The Seoul-Pyongyang hotline was opened on August 18, 1972 and maintained by the Red Cross. North Korea deactivated the hotline on March 11th 2013, as part of increasing tensions on the Korean peninsula.
See also 
- Derived from Federal Standard 1037C
- Egilsson, Haraldur. "The Origins, Use and Development of Hotline Diplomacy". Discussion Papers in Diplomacy. Retrieved 22 January 2013.
- The Independent—Monday, June 21, 2004--"India and Pakistan to Have Nuclear Hotline":
- Gienger, Viola (13 May 2011). "China-U.S. Defense Hotline Shows Gulf Between Nations". Bloomberg. Retrieved 5 March 2012.
- "Finally, a hotline between India and China". Ndtv.com. 2010-11-01. Retrieved 2012-01-21.