r to the components. And the lowly switch, manually operated at first, then later automated with the invention of the relay, became the basic parts of control systems. As alternating current (AC) evolved, control systems based on AC evolved. Ways were found to make relays open and close their 1 BASIC FUNDAMENTALS, DEFINITIONS, AND KEY TERMS switches with AC and perform the switching function just like DC- powered relays. Control systems behaved much like today's systems simply because the power to control machinery was either on or off. And perhaps that's where the idea or notion of a pulse came into the picture, simply the application of power for a specific time. Control systems still exist today, but they are far more complex and capable of exceedingly complex operations. An example being the glue logic mentioned earlier, or something like simple network management protocol (SNMP), which is far from simple. To survive, grow, and prosper in today's digital world you don't need to know much more about analog electronics. Analog circuits and systems are highly specialized and in limited use. They are likely to stay that way in the foreseeable future. If you're interested in learning more about analog audio and video, Luther5,6 and Robin are excellent references. Both authors have electrical engineering educations and television practice backgrounds. Luther's book gives a higher-level treatment of the subject, while Robin's is far more detailed. Digital is the here and now and likely to stay that way in the fore- seeable future, and there are some basics you need to know to survive. These include analog to digital conversion and digital to analog con- version, clock signals, pulse trains or digital streams, buffering and memory, parallel to serial conversion and serial to parallel conversion, bit stuffing and de-stuffing, timing and counting, system and network clocking, and synchronization. The Luther and Robin references also do a good job of introducing and teaching what you need to know about digital audio and