Mechanical switch to sound bell alarm.
Area shown with the two capacitors is a rope across the driveway 1 inch above the ground. At the left capacitor is metal eye hook bolt to connect the suspended rope passing through the "L" shaped support mounting bracket on left using the spring ( shown as the two coils) around the bolt shaft pressing against the bolt head ( the far right switch).
The action is simple. Tires of car press suspended rope down which makes bolt head at right come forward and press the two brass strips above the lamp (bell) together and ring alarm bell.
