Step 4: The Receiver
The receiver is so simple, a monkey could do it. All you have to do is solder the CdS photocell in series with the battery pack (3 volts), and then solder the two resulting leads to another mono jack. Use the biggest photocell you can find. Also note that it does not matter which way you connect the photocell; it has not plus (anode) or minus (cathode) sides.