Charges for these calls were high initially but declined greatly during the 20th century due to advances in technology liberalization.
The calls were transmitted by cable, communications satellite, radio, and more recently, fiber optics and Voice over Internet Protocol (VoIP).
International direct dialling was introduced in the 1970s, so calls can be dialed by country code without an operator.
There are now numerous ways for a mobile phone user to call internationally: A Local Dialling Disparity exists where the originating number and the foreign number are on the same network, usually a mobile telephone provider with operations in multiple countries.
A less expensive call path is available by routing within the local Mobile Switching Center without going out to the global GMSC to its HLR.