Blue Box

That's a picture of what used to be known as a blue box.  I suppose one of the first ones may have been blue, and it may have actually come in a box.
This one uses a Datamath calculator from Texas Instruments, and a speaker sitting over the mouthpiece of the handset to send dialing frequency tones. 
We used them in the early days of fax to access numbers that broadcast a on kilohertz tone for testing purposes.   They could also access number that would let you call long distance for free - of course, we never did that.