International telephone calls are those made between different countries. These telephone calls are processed by the telecom operators by means of using what is known as switches. The cost for international calls was very high initially but have declined greatly during the latter part of the 20th century due to advances in technology, namely VoIP (voice over internet protocol). An International VoIP call uses an internet connection as the transmission medium as opposed to the circuit-switched telephony used by the traditional Public Switched Telephone Network (PSTN). It does so, by sending voice data in small packets using IP (Internet Protocol). The use of VoIP technology allows International Calling and/or Long Distance providers to be very efficient on costs, reduce administrative overhead and hence, as a result, nowadays is very cheap to call internationally when compared to 20 or 25 years ago.