On some early automobiles both headlights went out when one bulb burned out. The headlights must have been connected in On some early automobiles both headlights went out when one bulb burned out. The headlights must have been connected in haste. series. perpendicular. parallel.
Wired in 'series' means there is only one path for current.....so when either light burns out, the circuit is broken and there is no path for current so the other light will be unlit
