Computers as Components, 3rd Edition

1.4 Design Example: Model Train Controller

In order to learn how to use UML to model systems, we will specify a simple system, a model train controller, which is illustrated in Figure 1.14. The user sends messages to the train with a control box attached to the tracks. The control box may have familiar controls such as a throttle, emergency stop button, and so on. Because the train receives its electrical power from the two rails of the track, the control box can send signals to the train over the tracks by modulating the power supply voltage. As shown in the figure, the control panel sends packets over the tracks to the receiver on the train. The train includes analog electronics to sense the bits being transmitted and a control system to set ...