| 摘要 |
A system selectively completes a horn circuit through which electrical power is provided to a horn in an automobile. A relay is connected to a power supply and completes the horn circuit when a current signal passing through the relay has at least a threshold magnitude. A relay driver is selectively activated by processing circuitry. When it is activated, the relay driver is in a conductive state, and when it is not activated, the relay driver is in a high impendance state. When the relay driver is in the conductive state, it places the relay in series with a low potential conductor thereby establishing the current signal at at least the threshold magnitude. The processing circuitry is electrically connected to a manually actuated sensor, which may be a flexible potentiometer. The processing circuitry activates the relay driver when the manually actuated sensor is actuated. The processing circuitry receives electrical power from the relay when the relay driver is in the high impendance state, but receives essentially no electrical power from the relay when the relay driver is in the conductive state. While the processing circuitry receives essentially no electrical power from the relay, the processing circuitry momentarily places the relay driver in the high impendance state so that the processing circuitry may receive electrical power from the relay and determine whether the manually actuated sensor is still actuated. An auxiliary power supply provides electrical power to the processing circuitry while electrical power is not received from the relay.
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