Codes and messages

Let us design a signal system with a partner. First ask: what messages do we need to send? Then imagine ideas: lights, sounds, or both. Plan a code with at most five signals. Build it: write the code on a card. Then test it by sending messages from across the room. The receiver tells the sender what the message was, and the sender says yes or no. Count how many arrived correctly out of the number sent. If some failed, improve the code: make signals more different, such as one clap and three claps instead of two claps and three claps. Test again and compare. Animals use signals too: whales send long sounds that travel far through the sea to reach other whales, which we can only describe in words. People also send signals with movement, such as a wave or a nod.