This section introduces the idea that coordination between different devices in a computer system always require that one of them starts the activity and sends signals to other devices. This starting device is called the initiator of the activity and the other device the responder. These roles may switch or change with future activities. The device that initiates an activity at one moment may turn around to be the responder in a subsequent transaction. Buses have to be controlled by one device at a time to avoid utterly electronic chaos. Deciding who is the initiator can be a tricky issue.