What is this brick and how do I use it? My son received a huge assortment of legos for his birthday and one piece we would like to know how to use, but I can't seem to find information on it anywhere! I would sure appreciate any help you fine folks might be able to offer. I am not able to share my picture because it's too big. The part I'm talking about is this one. The only words or numbers I can find on ours is "2002 lego group" and the numbers "2223". Thanks in advance. :)
This is 


Record and Play Module, 16 x 10 x 4 with Built-in Motors 4.5V (Item No: 3173c01)