Up to 10 students will be acting out the function at a time. I used 2" x 3" blank colored flashcards to create each of the 5 sets. In each set, there is a multiplication (or division) step, an addition (or subtraction) step, 4 inputs (with values for x) and 4 output cards (with no values).
One of the function machine students will have a multiplication (or division) job, while the other will have an add (or subtract) job. Input #1 will whisper their input to the mult/div student, who computes that operation and whispers the answer to the add/subtr student. That student will perform his/her operation and whisper the answer to output #1 student. Input #1 and output #1 will write their coordinate on the SMART Board and plot on a coordinate plane.
Aside from the obvious, this allows for many extensions: slope, linear equations, inverse operations, etc.