Digital electronics

We see the digits 0 to 9 on an electronic calculator or digital watch, but digital electronics has a much broader meaning. The circuits for digital applications operate with pulses of voltage or current, as shown in figure (a). A pulse waveform is either completely ON or OFF because of the sudden changes in amplitude. In between values have no function. Note that the ON and OFF states can also be labeled HIGH or LOW, or 1 and 0 in binary notation, which uses only two digits. Effectively, the digital pulses correspond to the action of switching circuits that are either ON or OFF.

Actually, all the possible variations in types of electronic circuits can be divided into just two types-digital circuits that recognize pulses when they are HIGH or LOW, and analog circuits that use all values in the waveform. The applications of digital electronics, including calculators, computers, processing, and data communications, possibly the biggest branch of electronics. Many other applications, including radio and television, use both analog and digital circuits. Analog-to-digital (A/D) converters in change the signal from one form to the other.

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Electric power

These applications are in the generation and distribution of 60-Hz ac power, as the source of energy for electrical equipment. Included are lighting, heating, motors, and generators.

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Communications electronics

This field includes AM radio, FM radio with stereo, and television with color. The equipment is divided between transmitters and receivers. Also, transmitters can be divided between radio-frequency equipment to produce the carrier wave radiated from the antenna and the audio and video equipment in the studio that supplies the modulating signal with the desired information. high-fidelity audio equipment can be considered with radio receivers. The receiver itself has audio amplifiers to drive the loudspeakers that reproduce the sound. Satellite communications is also a transmit-receive system using electromagnetic radio waves. The satellite just happens to be orbiting around the earth at a height of above 22,000 miles in order to have a tremendous field of view. Actually, the satellite is a relay station for transmitter and receiver earth stations.

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Application of Electronics

In addition to its use in radio and television, electronics is used in almost all industries for control functions, automation, and computing. There are so many applications that the broad field of electronics must be considered in smaller areas. Three logical groupings of electronics applications are defined here. Also included is a brief description of some important divisions with some typical job titles for working in the electronics business.

• Communications electronics
• Electric power
• Digital electronics

In addition to all the general applications in communications, digital equipment, and electric power services, several fields that could be of specific interest include automotive electronics, industrial electronics, and medical electronics. Both digital and analog techniques are used.

In automotive electronics, more and more electronic equipment is used in cars for charging the battery, power-assist functions, measuring gages, and monitoring and control of engine performance. Perhaps the most important application is electronic ignition. This method provides better timing of the ignition spark, especially at high speeds.

Industrial electronics includes control of welding and heating processes; the use of elevator control; operation of copying machines; metal detectors and smoke detectors; moisture control; and computer-controlled machinery. In addition, there are many types of remote-control functions, such as automatic garage door openers and burglar alarms. Closed-circuit television is often used for surveillance.

Medical electronics combines electronics with biology. Medical research, diagnosis, and treatment all use electronic equipment. Examples are the electron microscope and the electrocardiograph machine. In hospitals, oscilloscopes are commonly used as the display to monitor the heartbeat of patients in intensive care.

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Citizen's Band (CB) Radio

Forty 10-kHz channels from 26.965 to 27.405 MHz are available for public use of two-way radio. These CB channels are for class D service, with maximum power output of 4 watts (W). The CB transceiver includes a transmitter and a receiver. No operator's license is required for these personal radio services, often used in cars and boats.

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