Olivier Knox took a look at the history of the telephone of the American President:

• Before the American President has a phone call with another world leader, they are given a dossier with key information about their counterpart including their personality, the health of them and their family members, relationship issues, political pressures, and whether or not they like to joke.
• Scripts aren’t prepared beforehand although talking points often are.
• Each country has its own idiosyncrasies. Calls with the Chinese usually take a long time because they’re very formal and are required to start with a restatement of America’s Chinese policy. Sixty minute calls can have as little as 10 minutes of actual discussion of the issues at hand.
• The phone call can be made from anywhere in the White House, the Presidential plane and limousine, and, when the President is travelling, calls can even be made through guest telephones in hotel rooms – although the President has to be more careful about what they say then.
• Presidents generally prefer video conferences because it gives them key information about their counterpart’s body language. However only a few countries have the capability for secured videoconference – mostly those that America has helped set up the technology for.
• The calls aren’t recorded, although national security staffers listen in on the call and type up an internal, informal transcript that is kept secret. A summary is then sometimes released to the press.
• With some countries there is a race to release the summary of the call and frame the conversation in the media.
• The White House first got a telephone under President Rutherford B. Hayes in 1877. The number was “1”.
• Contrary to the myth popularized by Hollywood there was never a red telephone line between the White House and the Kremlin. It was initially a teletype connection and these days the connection involves the use of secured emails.

Read more about the foreign leaders who are able to get through immediately, those who are not, famous phone calls including the call in September 2013 to Iranian President Hassan Rouhaniy, and more over here.

Source: Yahoo News