An automatic switching unit for connection to a modem at a remote site in a data communications network. The switching unit normally connects the modem to a primary data transmission path. If the primary path malfunctions, a central site operator can telephone the remote site and establish a secondary...http://www.google.fr/patents/US4076961?utm_source=gb-gplus-shareBrevet US4076961 - Automatic switching unit for data communications network
Automatic switching unit for data communications network
