Film shows German troops surveilling the border with France from the Siegfried Line or Westwall, and when an alarm sounds the troops rush into combat positions. Likely a pre-war film.
See film XD8558, probably reel 2 of this film.
The Westwall was a series of fortifications constructed between 1938 and 1940 along the western frontier of Germany between the Netherlands and Switzerland. In WWII the Allies called it the Siegfried Line.