Covers switchboards which provide semi- and fully-automatic switching of local and distant calls on 2-wire and 2- and 6-wire lines and 2-, 4-, and 6-wire trunks utilizing space division switching matrices. Provides for interfacing with automatic central offices over 4-wire tone signaling trunks, 2-wire direct current (DC) closure trunks, and 5-wire recEive and transMit (E&M) trunks.