File:Magneto wall telephone 1917 open.jpg
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![File:Magneto wall telephone 1917 open.jpg](https://upload.wikimedia.org/wikipedia/commons/thumb/2/27/Magneto_wall_telephone_1917_open.jpg/660px-Magneto_wall_telephone_1917_open.jpg?20141021153811)
本预览的尺寸:660 × 600像素。 其他分辨率:264 × 240像素 | 528 × 480像素 | 845 × 768像素 | 1,126 × 1,024像素 | 1,518 × 1,380像素。
原始文件 (1,518 × 1,380像素,文件大小:215 KB,MIME类型:image/jpeg)
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[编辑]描述Magneto wall telephone 1917 open.jpg |
English: Early magneto wall telephone manufactured in 1917 by Julius Andrae and Sons Co., Milwaukee, Wisconsin, USA from an advertisement in a telephone trade magazine. Shown with case open revealing internal parts. Magneto for ringer is seen above the cylindrical batteries. Magneto telephones were "local battery" instruments; power for the transmitter was provided by dry cell batteries in each telephone, which had to be replaced periodically. These were superseded by modern "central battery" systems, in which all the power for the phone was provided by the local switching office. Alterations to image: Cropped out surrounding advertising copy and partially removed aliasing artifacts (crosshatched lines) added by scanning of halftone photo, using Gimp FFT filter. |
日期 | |
来源 | Retrieved October 20, 2014 from Telephony magazine, Telephony Publishing Co., Chicago, Vol. 73, No. 10, September 8, 1917, p. 33 on Google Books |
作者 | 未知Unknown author |
许可协议
[编辑]Public domainPublic domainfalsefalse |
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Carbon granule microphone (transmitter)
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Hand-cranked magneto (electric generator) generates ~ 100 V ringing current to ring remote phone's bell when initiating call.
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Moving iron diaphragm earphone (receiver)
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Electric bell ringer alerts owner to incoming calls. The bells themselves are on the outside of the front panel
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1.5 V dry cell batteries power the calling circuit
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"Hook switch" turns on the audio circuit when the receiver is lifted
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当前 | 2014年10月21日 (二) 15:38 | ![]() | 1,518 × 1,380(215 KB) | Chetvorno(留言 | 贡献) | User created page with UploadWizard |
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JPEG文件备注 | Created with GIMP |
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