Electrolytic Anti-Coherer DeForest-Smythe

In late 1900, along with W.W. Smythe, de Forest took out a patent for a

detector, and called it “the Electrolytic Anti-Coherer.” 

 

This detector was constructed like the filing coherer used by Marconi. There were two metal plugs contained in an insulated tube with a gap of about 1/100 inch between them. The gap was filled with one of several mixtures the inventors refered to as "goo". A typical mixture consisted of lead oxide, glycerine, water and metal fillings. The fillings were intended to act as secondary electrodes within the gap. Under the influence of a locally applied direct voltage crystalline lead is produced in such a paste and this builds up into chains and trees across the gap, like the silver particles in Schafer's plate. When a chain is completed deposition ceases as the gap is effectively short circuited. Once again a received pulse of oscillations breaks the chain causing a click to be heard in the telephone receiver which may be connected in the battery circuit.