It is not actually a phone, and it is not really red.
But in popular culture, the hotline between Russia and the US, formally known as the Washington-Moscow Direct Communications Link, is always referred to at the “red phone”.
This week, it was revealed that tensions rose between the US and Russia amid mounting evidence that Moscow had sought to influence the outcome of the presidential election, President Barack Obama used the so-called Red Phone to contact his counterpart, Vladimir Putin, and express his displeasure.
NBC News said that Mr Obama initially spoke to Mr Putin at the September G-20 G-20 summit in China, where he raised with him the hacking of Democratic National Committee emails – allegedly by hackers linked to the Russian government.
Not wanting to inflame the situation, Mr Obama reportedly used moderate language to warn Mr Putin of the consequences if Russian interference did not stop.
But when the hacking continued, Mr Obama resorted to the Cold War communication system to express his displeasure.
The network said that the red phone system, used to communicate in moments of crisis such as the September 11 attacks, was never actually a phone, but rather progressed from teletype more than 50 years ago, to the fax and now to email. The communication links the two counrties Nuclear Risk Reduction Centres.