Protected information transfer system

Abstract From the Canadian patent

An add/drop interface is connected in series with a data bus and is constructed for receiving an add/drop module. The add/drop interface includes a data selection multiplexer which receives through data from the data bus and add/drop data from the module and selects the proper output data in response to a signal received from a controller in said interface. The controller provides a signal to drive the data selection multiplexer to select the add/drop data only after all transient signals resulting from module connection have dissipated. The controller also provides error checking so that the through data is selected if errors are detected. Timing circuitry in the interface maintains the …