Complex sentence: The principle of operation of the electrical flash-lamp is linked to the shutter of an early box camera: tripping the shutter ignites the flash powder and releases the potential energy of the exploding powder causing a bright flash for indoor photography.
Split into simpler sentences: The principle of operation of the electrical flash-lamp is based upon when the shutter of an early box camera is tripped. This action then ignites the flash powder and releases energy of the exploding powder causing a bright flash for indoor photography.