Analog circuitry is constructed from two fundamental building blocks: series and parallel circuits. In a parallel circuit, all the components are connected to the same voltage, and the current divides between the various components according to their resistance. Digital circuits therefore can provide both logic and memory, enabling them to perform arbitrary computational functions. Memory based on the storage of charge in a capacitor, dynamic random-access memory (DRAM) is also widely used.) The design process for digital circuits is fundamentally different from the process for analog circuits. Basic electronic components may be packaged discretely, as arrays or networks of like components, or integrated inside of packages such as semiconductor integrated circuits, hybrid integrated circuits, or thick film devices.
Transistors interconnected so as to provide positive feedback are used as latches and flip flops, circuits that have two or more metastable states, and remain in one of these states until changed by an external input. The opposite of high tech is low technology, referring to simple, often traditional or mechanical, technology; for example, a calculator is a low-tech calculating device. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive electrical components and interconnection technologies.
This perception has led to high investment in high-tech sectors of the economy. Until 1950 this field was called "radio technology" because its principal application was the design and theory of radio transmitters, receivers, and vacuum tubes. The number of different analog circuits so far devised is huge, especially because a 'circuit' can be defined as anything from a single component, to systems containing thousands of components. Electronic components have two or more electrical terminals (or leads) aside from antennas which may only have one terminal. Digital circuits make extensive use of transistors, interconnected to create logic gates that provide the functions of Boolean logic: AND, NAND, OR, NOR, XOR and all possible combinations thereof. (In 2012 it was demonstrated that memristors can be added to the list of available components.) Analog circuits are very commonly represented in schematic diagrams, in which wires are shown as lines, and each component has a unique symbol. Students and faculty related with ENAEE or ABET accredited programs might be considered high-tech society members, regarding other traditional degrees. Similarly, an overdriven transistor amplifier can take on the characteristics of a controlled switch having essentially two levels of output. One rarely finds modern circuits that are entirely analog.