Abstract: A system wherein a plurality of remote stations, in response to a request from a primary terminal, will transmit requested data to the primary terminal and to a secondary terminal. The secondary terminal is operable to receive and process the data transmitted in synchronism with the requests from the primary, and without any synchronizing information between the primary and secondary terminals. This is accomplished with the provision of data processing means in the two terminals which have identical memory maps of the sequencing operation.

Abstract: A control station in data communication with a plurality of remote stations, each remote station including a receiving opto-isolator device and a transmitting opto-isolator device, each having an LED and an associated light detector. The LED of the receiving opto-isolator is in series circuit arrangement with the detector of the transmitting opto-isolator. A single remote station may be provided or a plurality of remote stations either in series or parallel circuit configuration. If in series configuration, a bypass circuit may be provided in the event of a failure of a particular remote station.