The Trimphone, first introduced in 1965, was a successful attempt to create a new style of telephone utilising new technology and materials, though remaining compatible with existing designs. It incorporated electronic tone ringing, and dial numbers illuminated from behind by radioactive tritium gas. The name was derived from these two features - Tone-Ringing-Illuminated-Model. Later examples had press-button keypads. This example, made by STC, shows the dubious result of obscuring a distinctive design with a leather cover in briefly-fashionable dark olive green.
© Science Museum / Science & Society Picture Library