Electrical and electronic drawing--Glossary

Actuator: A device that does the actual changing, if required, of a parameter (e.g., voltage) that has been sensed by the sensor and is being adjusted by the controller.

Address: An identifier or label of a discrete location in a computer’s memory. An address is composed of alphanumeric or numeric characters.

Alternating Current (AC): Current that flows in two directions.

ALU (Arithmetic Logic Unit): The heart of the microprocessor that performs the arithmetic, logical, and other related functions.

Ampere: The practical unit of current. One ampere will flow through a resistance of one ohm when a difference of potential of one volt is applied across its terminals.

Amplification: The process of increasing the strength (current, power, or voltage) of a signal.

Amplifier: A device used to increase the signal voltage, current, or power, generally composed of a transistor or vacuum tube and an associated circuit called a stage. It may contain several stages in order to obtain a desired gain.

Amplitude: The maximum instantaneous value of an alternating voltage or current, measured in either the positive or negative direction.

Analog-to-Digital Conversion: The process of converting varying analog signals to discrete digital signals. The acronym for Analog to digital conversion is A/D.

Anode: An electrode at which negative ions are discharged or from which the forward current (diode rectifier) flows.

Appliqués: Symbols and other graphical shapes printed on a sheet, which can be cut out and affixed to a drawing by moderate pressure.

ASCII: An acronym for American Standard Code for Information Interchange. It is the 8-bit (7, information; 1, parity) standard code for interchanging information between communication devices or circuits, where each letter, number, and control character has a discrete value.

Attenuation: The reduction in the strength of a signal.

Average: The average value of a quantity, such as average current.

Base: One of (usually) three regions of a transistor. Also one of the terminals of a transistor. In some transistors the base acts much like the grid of an electron tube. Baud: The speed at which discrete information is transmitted (bits per second in binary or half-dots per second in Morse Code).

Bias:

Vacuum tube: the difference in potential between the control grid and the cathode. Transistor: the difference in potential between the base and the collector. Magnetic amplifier: the level of flux density in the magnetic amplifier core under no-signal condition.

Binary Digit (bit): A numeral in binary arithmetic. Can have a value of one or, a bit may be represented as zero. (Also true or false, and on or off.)

Bipolar: One of two fundamental processes for the fabrication of integrated circuits. It involves the production of silicon layers having different electrical characteristics. Bistable: A circuit or circuit element having the ability to assume either of two states. Bug: An error in a computer program.

Bus: In a computer, a group (usually a multiple of 8) of parallel conductors (cables or

PC-board circuit paths), each carrying one bit of the binary data.

Busbar: A primary power-distribution point connected to the main power source. Byte: In computers, a series of 8 bits (see “Binary Digit”) of binary data.

CAD: Acronym for computer-aided design. The term used to be called computer-aided drafting.

Capacitor: A device consisting of two conducting surfaces separated by an insulating material or dielectric such as air, paper, or mica. A capacitor stores electric energy, blocks the flow of alternating current, and permits the flow of alternating current to a degree depending on the capacitance and frequency.

Cathode: An electrode through which a primary stream of electrons enters the inter- electrode space or to which the forward current flows (semiconductor).

Choke Coil: A coil of low ohmic resistance and high impedance to alternating current. Circuit Breaker: An electromagnetic or thermal device which opens a circuit automatically when the current in the circuit exceeds a predetermined amount. A circuit breaker can be reset.

Circular Mu: A unit of area equal to it/4 of a square mu, or 0.7854 sq mil. This is a unit of measure for wire sizes. (See Appendix D.)

Clock Pulse: A signal provided by the clock in a microprocessor to provide synchronization of other control pulses.

Clock Rate: How fast a clock operates, that is, pulses per second or frequency (e.g., 5 MHz).

Coaxial Cable: A transmission line consisting of two conductors concentric with and insulated from each other.

Cold Cathode: A cathode without a heater such as is found in most fluorescent lamps and some vacuum tubes.

Collector: That region of a transistor that collects electrons, or the terminal that corresponds to the anode (plate) of the electron tube in the normal mode of operation.

Commutator: The copper segments on the armature of a dc motor or generator. It is cylindrical in shape and is used to pass power into or from the brushes. It is a switching device.

Conductance: The ability of a material to conduct or carry an electric current. It is the reciprocal of the resistance of the material and is expressed in siemens (formerly called mhos).

Conductor: Any material suitable for carrying electric current. A conductor can be insulated (e.g., 120 V ac house cord) or noninsulated (e.g., some PC-board paths or large power conductors).

CPU: An acronym for the central processing unit which, essentially, is the heart of the computer. The CPU contains the ALU, registers, input-output circuits, and control circuits.

Cryogen (Cryogenic): A device that becomes a superconductor (has practically no resistance) at extremely cold temperatures. A circuit having such devices.

Current: The rate of transfer of electricity. An amount of electricity. The basic unit is the ampere.

Decibel: A unit (abbreviated dB) that expresses the logarithmic relationship between two signal power levels. Most often used to express power gain or attenuation. Deflecting Plate: That part of a certain type of electron tube which deflects the electron beam within the tube itself.

Detection: The process of separating the modulation component from the received signal.

Dielectric: An insulator; a term that refers to the insulating material between the plates of a capacitor.

Diffusion: A high-temperature process involving the movement of impurities into a silicon slice to change its electrical properties, used in fabrication of transistors, diodes, and ICs.

Digital-to-Analog Conversion: The process of converting discrete digital circuits to varying analog signals. The acronym for digital-to-analog conversion is D/A.

Diode:

Vacuum tube: a two-element tube that contains a cathode and plate. Semiconductor: a material of either germanium or silicon that is manufactured to allow current to flow in only one direction. Diodes are used as rectifiers and detectors. Direct Current (DC): Current that flows in only one direction.

Drain: One end of a channel in a field-effect transistor (FET). It compares with the collector of a bipolar transistor.

Duplex: In communication, data being transmitted and received simultaneously. Electric: A description of any circuit or system that uses electrical generation, transmission, and distribution equipment or devices.

Electrode: A terminal used to emit, collect, or control electrons and ions; a terminal at which electric current passes from one medium into another.

Electron: A negatively charged particle of matter.

Electron Emission: The liberation of electrons from a body into space under the influence of heat, light, impact, chemical disintegration, or potential difference.

Electronic: A description of any circuit or system that uses solid-state or vacuum-tube devices,

Emitter: That part or element of a transistor that emits electrons; it corresponds to the cathode of an electron tube, in the most common form of operation.

Energy: The capacity to do work or the work being done by a system. There are many types of energy (e.g., potential, electrical, magnetic, kinetic). It is measured in ergs, joules, kilowatts, and many or equivalent terms.

Epitaxial: A thin-film type of deposition for producing certain devices in microcircuits. It involves a realignment of molecules and hence has a deeper significance than simply thin-film manufacture.

Eyelet: Used on PC boards to make reliable connections from one side of the board to the other side.

Farad: The unit of capacitance.

Feedback: A transfer of energy from the output circuit of a device back to its input. Filament: An electrically heated wire that emits electrons or heats a cathode, which then emits electrons.

Filter: A combination of circuit elements designed to pass a definite range of frequencies, attenuating all others.

Frequency: The number of complete cycles per second existing in any form of wave motion, such as the number of cycles per second of an alternating current.

Fuse: A protective device inserted in series with a circuit. It contains a metal that will melt or break when current is increased beyond a specific value for a definite time period.

Gain: The ratio of the output power, voltage, or current to the input power, voltage, or current, respectively.

Gate: A device or element that has one output channel and one or more input channels whose state(s) determines (determine) the state of the output. The gate electrode of an FET which controls the current flow in the channel.

Grid: A wire, usually in the form of a spiral, that controls the electron flow in a vacuum tube.

Ground: A conductive connection with the earth to establish ground potential. Also, a common return to a point of zero potential. The chassis of a receiver or a transmitter is sometimes the common return and is, therefore, the “ground” of the unit.

Gun: The group of electrodes within a cathode ray tube (CRT) that emits the beam of electrons.

Henry: The basic unit of inductance. The inductance of a circuit is one henry when a current variation of one ampere per second induces one volt. (The plural is henrys.)

Hole: In semiconductors, the space in an atom left vacant by a departed electron. Holes flow in a direction opposite to that of electrons, are considered to be current carriers, and bear a positive charge.

Impedance: The total opposition offered to the flow of an alternating current. It may consist of any combination of resistance, inductive reactance, and capacitive reactance.

Inductance: The property of a circuit or two neighboring circuits which determines how much electromotive force will be induced in one circuit by a change of current in either circuit.

Inductor: A circuit element designed so that its inductance is its most important electrical property; a coil.

Integrated Circuit (IC): A circuit in which devices of several different types such as resistors, capacitors, and transistors are made from a single piece of material such as a silicon chip and are then connected to form a circuit.

Inverters: Devices used to change direct current to alternating current.

LED: A diode that emits light when current is passed through it.

Light Pen: A photosensitive pen-like device, used primarily in CAD, that can cause the computer to change or modify the display on a CRT.

Logic: The arrangement of circuitry designed to accomplish certain objectives such as the addition of two signals. Used largely in computer circuits, but also used in other equipment such as automated machine tools and electric controls.

Magnetron: A vacuum-tube oscillator containing two electrodes, in which the flow of electrons from cathode to anode is controlled by an externally applied magnetic field.

Micron: One millionth of a meter, now called a micrometer in the International System of Units (SI).

Modem: An electronic device that performs the functions of modulation and demodulation required by communications.

Modulation: The process of varying the amplitude (amplitude modulation), the frequency (frequency modulation), or the phase (phase modulation) of a carrier wave in accordance with other signals in order to convey intelligence. The modulating signal may be an audio-frequency signal, video signal (as in television), electric pulses or tones to operate relays, or similar.

Mylar: A trademark used for a type of polyester film or sheet that is used for magnetic tape and capacitor dielectrics and as a drawing medium.

Nibble: In computers, a series of 4 bits of binary data (half a byte).

Oscillator: A circuit that is designed to generate an audio or radio frequency; a mode of amplification. Also the main device in such a circuit.

Oscilloscope: An instrument for showing, visually, graphical representations of the waveforms encountered in electric circuits.

Overload: The condition where the electrical or electronic circuit is drawing more current than normal. Depending on the size of the overload, the circuit may be interrupted by a protective device such as a fuse or a circuit breaker.

Peak: The maximum instantaneous value of a quantity, such as peak power.

Permalloy: An alloy of nickel and iron with an abnormally high magnetic permeability.

Photoconductivity: Property of a device or material to experience a change in conductivity on exposure to light.

Pinboard: A board given to drafters that contains equipment plan views pinned in a particular arrangement. From this pinboard, a drafter can make a layout.

Pixel: The smallest dot being displayed on a CRT screen. A greater number of pixels per unit area allows more resolution.

Plate: The principal anode (electrode) in an electron tube to which the electron stream is attracted. Also, one of the conductive electrodes in a capacitor or battery.

Potential: The degree of electrification as referred to some standard such as the earth. The amount of work required to bring a unit quantity of electricity from infinity to the point in question.

Potentiometer: A variable-voltage divider; a resistor which has a variable contact arm so that any portion of the potential applied between its ends may be selected.

Power: The rate of doing work or the rate of expending energy. The unit of electric power is the watt.

Printed Circuit: A circuit in which the wires have been replaced by conductive strips on an insulating board, abbreviated with uppercase letters, PC.

Raceway: Any channel for enclosing conductors which is designed expressly and used solely for this purpose.

RAM: Acronym for random-access memory, which is memory that can be written to (data inputted) or read from (data outputted).

Relay: An electromechanical or electronic switching device that can be used as a remote control, usually to open or close a circuit.

Resistance: The opposition that a device or material offers to the flow of current. It determines the rate at which electric energy is converted into heat or radiant energy (the basic unit is ohms).

Resistor: A circuit element whose chief characteristic is resistance; used to oppose the flow of current.

Resonance: The condition existing in a circuit in which the inductive and capacitive reactances cancel each other.

ROM: Read-only memory which permits only reading from memory as opposed to RAM, which is both read and write memory.

Saturation: The condition existing in any circuit when an increase in the driving signal produces no further change in the resultant effect.

Semiconductor: An element, such as germanium or silicon, from which transistors or diodes are made; the device itself. The resistivity of the element is in the range between those of metals and insulators.

Simplex: In communications, data being either transmitted or received but not simultaneously.

Sensor: A device that measures a change in a parameter (e.g., voltage) and sends this information to some type of recorder, controller (e.g., computer, programmable controller), or both.

Solenoid: An electromagnetic coil that contains a movable plunger.

Synchronous: Happening at the same time; having the same period and phase. Tachometer: An instrument for indicating revolutions per minute.

Terminal: A combination of an output CRT (display) and an input keyboard. Thick-Film Circuit: A film-type circuit. The range of thickness of deposited patterns is from 0.01 to 0.05 mm.

Thin-Film Circuit: A circuit made by depositing material on a substrate, such as glass or quartz, to form patterns that make devices, such as resistors and capacitors, and their connections. The thickness of the film forming these devices is only a few micrometers (0.001 mm).

Thyristor: A bistable semiconductor device having three or more junctions that can be switched from OFF to ON or vice versa. Silicon-controlled rectifiers and triacs are in this class.

Transducer: A device that converts an input into a different type of output. Examples are microphones, speakers, lamps, vibrators, strain gauges, pneumatic to electric (pie), and so on.

Transformer: A device composed of two or more coils linked by magnetic lines of force; used to transfer energy from one circuit to another (i.e., mutual coupling between circuits).

Triode: A three-electrode vacuum tube containing a cathode, control grid, and plate. Also a three-region semiconductor.

Volt: The unit of voltage, potential, or electromotive force (emf). One volt will send a current of one ampere through a resistance of one ohm.

Voltage: Used interchangeably with potential. (See “Potential.”)

Watt: The unit of electric power. In a direct current one watt is equal to volts multiplied by amperes. In an alternating current the true power in watts is equal to effective volts multiplied by effective amperes.

Word: In computers, a series of one to several bytes. Word length is expressed in bits and bytes, such as a 2-byte word = a 4-nibble word = a 16-bit word. Word length is not standard.

Electrical Part (Device) Reference Designations

FROM ANSI Y32.2-1975

* Those parts marked with an asterisk (*) are also approved in the Federal Item Identification Guide Cataloging Handbook H6- 1.

The preceding list is not the complete list of devices shown in ANSI Y32.2-1975. This listing contains more commonly used parts. This listing or ANSI Y32.2- 1975 does not contain device function designations for power switchgear, industrial control, and industrial equipment. For these function designations, please consult:

1. American National Standard Manual and Station Control, Supervisory and Associated Telemetering Equipment, C37.2- 1970.

2. NEMA Standard, Industrial Controls ICS- 1970 (R1 975)

3. Joint Industrial Council Electrical Standards for Mass Production Equipment, EMP-1-1967 and General Purpose Machine Tools, EGP-l-1976

4. Military Standard, Designations for Electric Power Switch Devices and Industrial Control Devices, MIL STD 27

Control-Device Designations

Abbreviations for Drawings and Technical Publications

Primarily from MIL STD 12D and other sources where Mu Std 12D does not list an abbreviation.

Note. These symbols are authorized for use in drawings for the Military and in specifications; however, there are abbreviations listed here that are not formed in Mil Std 12D. Therefore, the authors use their preferred abbreviation. A similar list has been compiled by the American National Standards Institute. The preceding list is not the complete Military Standard; actually, there are approximately 10,000 abbreviations in the standard. If in doubt about abbreviation, spell out the word.

The Frequency Spectrum

Note: The current IEEE and international standards utilize the term hertz for cycles per second.

Thus KC (old form) becomes kHz, MC (old form) becomes MHz, etc.; kHz represents kilocycles; sMHz, megacycles; and GHz, giga-cycles (1 billion cps).