This was a great technical advance when it was introduced by the Post Office as Type 162 in 1929, after joint development with the Siemens company. The phone used new circuitry, a new kind of microphone and an improved receiver to give louder, better quality speech over longer lines. The microphone, unlike that in the famous 'candlestick' phone, would work when tilted to any angle and so could be incorporated into the simple one-piece handset we take for granted today. It was also one of the first to make extensive use of plastics.