Patent ID: 6522689
Filing Date: 2003-02-18
Classification: H04L

Abstract:
A monitoring circuit for a data transmission network having a plurality of transmissive and receptive network nodes and a double-line bus connecting the network nodes and serving for redundant double transmission of digital communications and having a first line and a second line via which communication pulses transferred in the form of time-spaced pulse sequences are transferred in synchronous manner in terms of time slot, the circuit comprising:a) at least one of the network nodes is configured to confirm the reception of the respective pulse sequence by sending a confirmation pulse during a predetermined time slot that is equal for all network nodes; b) in at least one of the network nodes the first line (A) is connected via a first resistor to a network-node-inherent operating potential source and via a first controllable switch to a reference potential source, and the second line (B) is connected via a second resistor to the reference potential source and via a controllable second switch to the operating potential source; c) the first and second switches are configured to simultaneously switch to a non-conducting state for transmitting a communication pulse having a first logic value and to simultaneously switch to the conducting state for transmitting a communication pulse having a second logic value; d) a potential change detector is coupled to the two lines (A, B) to monitor for the presence of potential change activities and detect a condition in which, during a pulse sequence, potential change activities occur only on the first line, but not on the second line; e) and a first time measuring circuit is coupled to the potential change detector and is configured to measure the duration of the condition, and when a predetermined duration of such a condition is exceeded, to generate an error signal, and to cause the second switch of the at least one network node to switch to the non-conducting state.