An evolution of Alexander Graham Bell's Photophone, developed in 1880, using a modulated infra-red light beam to transmit audio signals. Though passed over by civilian consumers in favor of radio, one of the photophone's greatest flaws became a massive virtue for military use; because the beam could only hit a single receiver, it was impossible to intercept a transmission without physically obstructing line of sight between the two units, making it one of the most secure ranged communication devices of the era. Measuring 11 inches long and 7 1/2 inches wide, with the Carl Zeiss plaque dated 1940 and a Nazi Waffenamt stamp below the front apertures, a swiveling pintle mount on the underside, and controls on the rear. With a black leather transport case, stamped "Li Spr 80" on the lid and dated 1940 on the body.