It had a steel core, with a copper ribbon wound spirally around it, and tinned to the core wire. 弗兰克·刘易斯·戴尔.爱迪生的生平和发明.
Generally speaking, this consists of a motor-driven cylinder having metallic pins placed at intervals, and arranged spirally, around its periphery. 弗兰克·刘易斯·戴尔.爱迪生的生平和发明.