The article links to the Wikipedia page, which is a good starting point. > Signalling System No. 7 (SS7) is a set of telephony signaling protocols developed in

The article links to the Wikipedia page, which is a good starting point. > Signalling System No. 7 (SS7) is a set of telephony signaling protocols developed in 1975, which is used to set up and tear down most of the world's public switched telephone network (PSTN) telephone calls. It also performs number translation, local number portability, prepaid billing, Short Message Service (SMS), and other mass market services. https://en.wikipedia.org/wiki/Signalling_System_No._7 https://en.wikipedia.org/wiki/Signalling_System_No._7