On January 26, 1926 (see Fig. 1 ), John Logie Baird gave a demonstration at his laboratory in 22 Frith Street, London, of the live transmission of moving images, obtained in reflected light with tonal graduation, to members of the Royal Institution. This event is generally accepted as the first public demonstration of true television [1] , [2, pp. 88–107] , [3, pp. 65–84] . Ten months earlier, on March 25, 1925, Baird had demonstrated the televising of moving silhouette images, at Selfridge’s department store, on Oxford Street in London [2, p. 57] , [3, p. 75] . What had changed in those ten months to enable Baird to televise a sufficient tonal range of moving human faces? This article describes the set of events which led up to Baird’s accomplishment and answers the question concerning the technology employed.

中文翻译：

---

John Logie Baird 和盒子里的秘密：世界上第一次公开电视演示背后的未被发现的故事

1926 年 1 月 26 日（见图 1），约翰·洛吉·贝尔德在他位于伦敦弗里斯街 22 号的实验室向皇家学会的成员演示了在反射光中获得的动态图像的实时传输和色调分级. 这一事件被普遍认为是真实电视的首次公开展示 [1] , [2, pp. 88–107] , [3, pp. 65–84] 。十个月前，也就是 1925 年 3 月 25 日，贝尔德在伦敦牛津街的塞尔弗里奇百货公司演示了移动剪影图像的电视转播 [2, p. 17]。57], [3, p. 75]。在这十个月里发生了什么变化，使贝尔德能够在电视上播放足够多色调的移动人脸？本文描述了导致贝尔德取得成就的一系列事件，并回答了有关所采用技术的问题。