Used to connect or switch other devices by means of the installed, potential-free relay point 1 x change over (max. 3A) after key depression and disconnects them again automatically at the end of the adjusted time. The time lapse may be stopped at any time by pressing the second key. Use: automatic time switch for staircase lighting, for exposure devices, alarm devices, electric toys etc. In addition a potentiometer 1M lin. and 2 push-buttons for "Start" and "Stop" are required.