DIY assembled telegraphs receiver transmitter kits set,educational science DIY experiments toy. Principle : electric energy (4*AA Batteries needed;Battery is not included)product radio waves,receiver is connected to raise the alarm after receiving the radio. Including parallel or series circuit,electrode principle and radio waves tips for kid child learning studying. Develop children's hand & eye coordination, and help children experience the of power, expand kids scientific & mechanical interest. Great scientific experiments lab teaching aids school supplies,Cool designed DIY scientific toy gifts . Specification:Need to be assembled by yoursel. Colour:Photo Color Material:wood + plastic + electronic accessories Finished size: 60 x 100 x 20mm Package Contents: 1 Wireless Telegraph Receiver Transmitter Module Kit (This is just a DIY kit, not a finished product; Battery is not included) Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.