This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Marconi coherer tube Rankin Kennedy Electrical Installations Vol . Drawing of coherer radio wave detector used in the first radio receivers from about to The coherer was invented by Edouard Branly in but this widely used design was perfected by Guglielmo Marconi around It consists of an evacuated glass tube with two electrodes