Automotive vehicle electrical load supervisory system

Claim 1

In an automotive vehicle having headlight lamps (20, 32), a battery (23), electrical supply lines (21, 33) connecting the battery (23) to the headlights (20, 32) and a switch (22) interposed between the battery and said supply lines to selectively connect, or disconnect current flow from the battery through the supply lines to the headlights; an electrical supervisory system to monitor current flowing through said supply lines (21, 33) to the headlights (20, 32) comprising at least one ferrite core having at least one opening therethrough and having an approximately square hysteresis characteristic, the supply line (21, 33) to at least one of the headlights (20, 32) passing through an opening of the core, the core being saturable upon current flow through the supply line when the switch (22) is closed; a test signal wire (28, 39) passing through an opening of the core; a read signal wire (25) passing through an opening of the core; an a-c source (29) connected to the test signal wire; a headlight defect indicator means (27); and an AND-gate (37), the read signal wire (35) being connected to one input (36) of the AND-gate, and the battery (23) being connected through the switch (22) to the other input (38) of the AND-gate (37), the output of the AND-gate (37) being connected to the indicator means (27), to energize the AND-gate upon conjunction of: (a) closing of the switch (22) and hence energization of the supply lines (21, 33) to the headlights (20, 32) and (b) failure of current flow to at least one of said headlights by energization of the read signal wire (35) by transformer action from the test signal wire upon non-saturated condition of the core due to lack of current flow through the respective supply line (21, 33) to the respective headlight (20, 32), and to isolate the indicator means from the read signal wire (35) when the switch (22) is open.