例句與造句

1. In 1903, Alfred Wehrsen patented an ebonite rotating disk possessing embedded sectors with button contacts at the disk surface.
2. When the normally open push button contact closes and the normally closed obstruction detector is closed ( no obstruction detected ), electricity is able to flow to the motor which closes the door.
3. It's difficult to find button contact in a sentence. 用button contact造句挺難的