Computers as Components, 2nd Edition

1.4 Model Train Controller 37

There will be one instance of the Console class and one instance of each of the

component classes, as shown by the numeric values at each end of the relationship

links. We have also shown some special classes that represent analog components,

ending the name of each with an asterisk:

■ Knobs* describes the actual analog knobs, buttons, and levers on the control

panel.

■ Sender* describes the analog electronics that send bits along the track.

Likewise, the Train makes use of three other classes that define its components:

■ The Receiver class knows how to turn the analog signals on the track into

digital form.

■ The Controller ...