関連ワード:  when was the first cordless phone invented    when was the first portable phone invented    when was the first wireless phone invented    when was the first cordless home phone invented    when was the first wireless telephone invented    when was the first portable telephone invented    when was the first portable cell phone invented    when was the first wireless cell phone invented    when was the first wireless phone call made    when was the first wireless phone charger made  
結果 : when was the first cordless phone invented