Known as the Ashkir-Jobson Communigraph it consists of a small table with a free moving pendulum underneath.
The pendulum may then make contact with some small metal plates that represent the alphabet.
The contact closes a circuit and makes a corresponding letter appear illuminated upon the table.
No medium is necessary for this instrument to work.
A circle is formed around the table.
The pendulum starts swinging on it`s own accord.
Divination
Exploring Scrying: How to Divine the Future and Make the Most of It (Exploring Series)
Paralumun New Age Village