Signaling used in Public Switched Telephone Networks (PSTN) calls relate to the telephony signals which circulate the globe irrespective of international boundaries. In order that telephone services providers are able to communicate at an international level it has been necessary for their engineers to interact with those in other countries. Appreciating what an engineer operating in a foreign country is talking about may not be immediately obvious and because advances in technology were looming closer on the horizon in 1975 AT&T began to define what have developed into standard protocols that could be recognized at an international level. Even so the references adopted are not always immediately recognizable to anyone who operates outside the engineering environment for example in the United States SS7 is referred to as CCS7 and in the UK C7 (CCITT number 7).