U-1901: United Kingdom
3 1/4" X 3 1/4" (78mm X 78mm)
No markings
Picture courtesy Gene Kingsley |
These are known as radio relay insulators. They were a unique style used by a company called Rediffusion. Rediffusion was the trading name of Broadcast Relay Service Ltd, formed in 1928. In 1929 the company introduced its first cable radio service in Hull to customers frustrated with the difficulties of tuning in weak radio broadcasts. With the arrival of the first experimental television broadcasts in the 1930s, Rediffusion began supplying an early form of cable TV service to its customers with a pause in television broadcasts during the Second World War.
U number assignment by Bob Berry April 2016.