horn speaker is 20 or 30 dollars amp is 10 dollars plus a cheap mp3 player another 30 or 40 dollars plus time and materials (soldering iron solder speaker wire 3.5mm jacks) it adds up in a hurry. its better to go with a pm4 or a cheap economic caller i made one and it worked but was a hassle unwinding and winding the 50 foot cord on every stand plus it would tangle. stick to hand calls or buy a pm4.