PARASITIC POWER SUPPLY FOR A SIGNALISED TRAFFIC INTERSECTION

摘要

A parasitic power supply (8) adapted to draw off power from electricity sources available at signalised traffic intersections and supply power to auxiliary devices (16) installed in close proximity to the intersections is disclosed. The power supply (8) includes an auxiliary power path (14) connected between the power line (15) supplying power to a signal lamp (5) and the auxiliary device (16), which includes a fail-secure switch (17) connected therein. A control circuit (18) forming part of the power supply is adapted to sense a load current being delivered to the signal lamp (5) and to open the switch (17) when the load current to the lamp drops below a predefined minimum value, thereby interrupting the auxiliary power path (14) and flow of electricity between the power line (15) and the auxiliary device (16).