Abstract: Data communication in an electrical system according to the present invention uses the time difference between two successive current or voltage pulses to represent different data values. The time differences (?t9??t16) can assume more than two different predetermined values, and thereby each pulse can represent more than one data bit. A central unit of the inventive system transfers data to a number of nodes by modulating voltage pulses onto a base voltage supplying power to the nodes. The time difference (?t9??t12) between successive voltage pulses represents a data value. The nodes transfer data back to the central unit using current pulses, whereby the time difference (?t13??t16) between the latest voltage pulse and the current pulse represents the data sent to the central unit. Data from two or more nodes are possible to transfer simultaneously without disturbing each other. The base voltage on the bus can be AC or DC.

Abstract: A bus system comprises a data bus (10), a central unit (20) and a number of input (30A-B) and output (40A-D) nodes. The system is arranged such that nodes (30A-B, 40A-D) changing their states, automatically report this to the central unit (20). The central unit (20) is put into a particular node association mode. When being in this mode, the central unit (20) detects two consecutive messages (M 10, M11) of state changes at connected nodes (30A-B, 40A-D), and creates an association between the nodes (30A, 40D) as a response. The association is thereby possible to create by deliberately changing the state of the nodes that is wanted to be associated. The central unit (20) may be brought back to normal operation mode either automatically, or by an action by the operator. In this way, one or several input nodes (30A-B) can be associated with one or several output nodes (40A-D).

Abstract: Data communication in an electrical system uses the time difference between two successive current or voltage pulses to represent different data values. The time differences (?t9??t16) can assume more than two different predetermined values, and thereby each pulse can represent more than one data bit. A central unit transfers data to a number of nodes by modulating voltage pulses onto a base voltage supplying power to the nodes. The time difference (?t9??t12) between successive voltage pulses represents a data value. The nodes transfer data back to the central unit using current pulses, whereby the time difference (?t13??t16) between the latest voltage pulse and the current pulse represents the data sent to the central unit. Data from two or more nodes are possible to transfer simultaneously without disturbing each other. The base voltage on the bus can be AC or DC.