Hauck Polychron - how to use

Hello!
In the scholl darkroom, where I teach photography there is a Hauck Polychron timer, which I think is broken. I have used this type of timers before - you set the hands to desired time, and after reaching that time the hands stop moving and the clock beeps. Well this particular timer doesn't stop at all. The hands are moving endless until I press the stop button. Is the timer broken, or I am doing something wrong? Does anyone who has a manual for this timer can send it to me?
Greetings and thanks for your help
Jerzy Łapiński

.This clock is unknown to me,but from the photos on the net it is obvious that

-) you can chose between different small scales that are pushed via their slit over the hub
(Don't ask me how the clock realizes the different scales...)

-) you have to put sliders at the respective figures to make that pin above that scale actuate a switch