A bake­lite tray con­tain­ing 20 glass slides can be insert­ed by flip­ping down the front of the view­er, then, by mov­ing a knob, locat­ed on the right side, up and down, one slide after anoth­er can be exam­ined. The slides are pulled up by mag­nets which con­nect to met­al strips attached to the glass slides. Below the knob, a brass arrow will point to the num­ber of the slide that’s in view and allows nav­i­ga­tion to a spe­cif­ic slide. For that, the knob has to be stopped at an inter­me­di­ate posi­tion, which unlocks the tray move­ment. This posi­tion is also required to exchange the tray.
Due to the design of the bake­lite trays, it is pos­si­ble to insert both 45x107mm and 6x13cm slides into the same mech­a­nism. There­fore, this ‘Planox Uni­versel’ is a bi-for­mat ver­sion with an addi­tion­al lever on the left side of the hous­ing to switch between 6x13cm and 45x107mm, because the slides in the small­er for­mat need to be stopped at a low­er lev­el than the larg­er ones. An addi­tion­al mask­ing-frame for the small­er slides can be hung right in front of the magnets.
The stor­age cab­i­net con­tains ten draw­ers hold­ing six trays each, result­ing in a capac­i­ty of 1200 slides in total. The top of the cab­i­net can be shift­ed for­ward allow­ing a more com­fort­able sit­ting posi­tion when using the viewer.
There is also an elec­tric light­ing unit that can eas­i­ly be hung on the back of the viewer.