| 摘要 |
PURPOSE:To attain a call accurately and easily by lighting a powered-on filament to close up a call code character on a pushbutton upper face sharply. CONSTITUTION:The inside of a button 1 is made hollow and vacuum and a filament 2 is incorporated therein. In lifting up a handset to use a telephone set, the switch is turned on automatically and the filament 2 incorporated in the button powered on. The powered-on filament 2 is lighted immediately and the call code character 5 on the upper face of the button is lighted sharply.
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