Be on the lookout
Many students think that a set of instructions is transmitted rather than a signal that can be used to set off a stack. In other words, students sometimes expect to send a whole program via infrared, just as a program is downloaded to the RCX.
What you can do: Help students by drawing an analogy to a person receiving a signal or a password rather than a set of instructions. The person knows what to do when he or she receives the signal. The signal just tells the person “do it now,” the person already knows what “it” means. For example, tell a student to raise her hand each time she hears the number 87. Explain that the receiver already has the instruction to raise her hand. She’s just waiting for a signal to set off that instruction.
Use Transparency #9 to help guide a discussion about sending messages.