Coherer, one of two

1885-1940

Iron borings coherer (Branly type), 1894

1894

Iron borings coherer (Branly type), 1894

1894

Branly tripod coherer, 1900-1910

1900-1910

Coherer, one of two

1885-1940

Two iron boring coherers (Branly type), 1894

1894