DiSEqC (Digital Satellite Equipment Control) is a communications protocol specified by Eutelsat and used widely in Digital consumer Satellite Receivers.
These versions of the protocol specify a unidirectional communication to attached devices. Superceeded by DiSEqC2.x.
With DiSEqC2.x it is possible to auto-configure Satellite Dish Equipment, meaning complicated config dialogs on the OSD are not necessary anymore. The SetTopBox can directly probe the DiSEqC Bus for available devices like Switches and LNBs and request the LNB LOF.