Transparent 700-type telephone : a clear view of technology

What happens inside a phone is a question that's been asked ever since the first phones were enclosed within wooden boxes. There's an element of magic that allows two people to talk hundreds of miles apart and people have always been curious as to how it works.

The Post Office started a trend to let people in on the secret in the 1930s. Manufacturing with plastics meant that transparent models could be made of standard phones. They were taken to shows (such as the ideal home show), exhibitions and placed in shop windows.

People learnt how they worked or what changes had gone into new models and it was a useful way for the Post Office to justify subscription charges, once a subscriber understood the level of technology in their phone. The phones were never put on general distribution, in fact only about two dozen of these particular transparent 700 models were ever made.