Abstract: A teaching device, for use in a classroom, comprising a hand-held size calculator adapted to normally include a display for showing the numerical output of the calculator, and adapted to include a face plate having a plurality of keys which are arranged in a particular pattern and which bear indicia indicating the calculator function of the keys. The calculator does include a circuit for producing a signal in response to depression of the face plate keys of the hand-held size calculator. The teaching device further includes an enlarged keyboard including a plurality of enlarged keys arranged in a key pattern simulating the face plate keys of the hand-held size calculator, and indicia on the enlarged keys simulating the indicia on the faceplate keys of the hand-held size calculator. The indicia is readily readable anywhere within the classroom. The keyboard also includes a plurality of switches responsive to depression of the keyboard keys.