| 摘要 |
The control centre (1) is connected to all connected devices for controlling or monitoring, briefly called controllers (3), by means of a two-conductor data bus (2) which is only fed with voltage from the control centre (1). Each controller (3) and the control centre (1) have a receiving and a transmitting device (7, 8) for messages. Each transmitting device (8) consists of the series circuit of a fusible link (12), a transistor (13) and an inductive resistance (14). The voltage UH is present as a digital H on the data bus (2). When the data bus (2) is loaded with a low impedance by one of the transmitting devices (8), the voltage drops to UL as a digital L. A disturbance by continuous low-impedance loading of a transmitting device (8) prevents any exchange of messages but also causes the control centre (1) to feed in a higher power to the data bus (2). This destroys the corresponding fusible link (12) and enables traffic with the remaining controllers (3) to be continued. <IMAGE> |
