https://www.cisco.com/c/en/us/support/docs/routers/3600-series-multiservice-platforms/12444-2fxo-vic.html?referring_site=bodynav
Understanding Foreign Exchange Office (FXO) Voice Interface Cards - Cisco
The Cisco Foreign Exchange Office (FXO) interface is an RJ-11 connector that allows an analog connection to be directed at the public switched telephone...
foreign exchange officevoice interfaceunderstandingfxocards