Patent ID: 7647439

Claim:
An electronic warning system, comprising: a two-core circular bus; and a plurality of bus users, the circular bus extending through and connecting the bus users and supplying voltage and communication to the plurality of connected bus users, each bus user comprising: two pairs of terminals; a bus user circuit connected in series with the two-core circular bus via the two pairs of terminals, the bus user circuit being configured to receive a supply voltage and to measure the voltage and signs on the connected bus cores; and first and second polarity-reversal protection bridges connecting the bus user circuit to each of the cores of the circular bus, wherein the bus user circuit is connected in parallel between d.c. output terminals of the protection bridges, each bridge including: a branch comprising four FETs (field effect transistors) with parasitic diodes polarized in the direction of current-flow, thereby initializing the FETs in a non-conducting state; wherein the bus user circuit is further configured to control the FETs of the first and second protection bridges in response to a supply voltage being applied to at least one of the polarity-reversal protection bridges.