Electronic Engineering Dictionary

Symbol. A signal state within a defined time interval that is recognized as distinct from another symbols.

Symmetrical Multivibrator. A circuit that generates square waves. Also refer to Definitions of Transistor Multivibrator Circuits.

Symmetrical Pair. A balanced transmission line, in a multipair cable, having equal conductor resistances per unit length, equal impedances from each conductor to earth, and equal impedances to other lines.

Synchro. A small motor-like analog device that operates like a variable transformer. A synchro converts an angular position received as an input into an electrical output. The diagram shows the stator and rotor of a synchro; Schematic diagram of a synchro.

Synchro Schematic

Synchro Capacitor. A unit containing three delta-connected capacitors. The synchro capacitor is used in synchro systems to increase the systems accuracy by cancelling or reducing the phase shift introduced by synchro inductance. Also refer to Definitions of Capacitor Terms.

Synchro System. Two or more synchros interconnected electrically. The system is used to transmit data among equipments and stations.

Synchro Tester. A synchro receiver with a calibrated dial. This receiver is used primarily for locating defective synchros. It can also be used for zeroing synchros.

Synchronizer. A clocking circuit that supplies timing pulses to another circuit. A buffer circuit that compensates for the differences in the data rate between two different circuits, as in a FIFO. A circuit that supplies timing signals to other radar components.

Synchronizing Network. A circuit, also called a crossover or switching network, used in servo-systems to sense how far the load is from the point of correspondence; it then functions to switch the appropriate signal into control.

Synchronous. One or more circuits operating under the same clock relationship.

Synchronous Logic. A circuit that operates with synchronous timing, a clock. In general a synchronous system is slower than an asynchronous system because the circuit has to wait for a clock before making a change in the output. While a circuit with out a clock is able to change its output using the same asynchronous inputs as a synchronous circuit, with out having to wait for the clock to arrive.

Synchronous Counter. A counter with an output that only changes after receiving a clock pulse. Examples; 74F161 Binary Counter, 74F191 Decade Counter. Also see 54F192 Synchronous Counter details.

Synchronous Motor. An ac motor whose rotor is activated by dc. It is characterized by constant speed and requires squirrel-cage windings or some other method to be self-starting. [Motor Manufacturers]

Synchronous Orbit. An orbit in which the satellite moves or rotates at the same speed as the earth.

Synchronous Speed. The speed at which the rotating field in an ac motor revolves. This speed is a function of the number of poles in the field and the frequency of the applied voltage.

Synchronous Transmission. Transmission between a driver and receiver that operate at the same frequency and are locked in phase by a common clock, timing bits, bit encoding or some other timing correction operation.

Synchronous Tuning. In a klystron amplifier, a method of tuning that tunes all the resonant cavities to the same frequency. High gain is achieved, but the bandwidth is narrow.

Sync-Signal. The output from a Synchronizer, used as a timing pulse.

Syntax. The make up of expressions or the rules that govern a language. In a language, the relationships among characters or groups of characters, independent of their meanings or the manner of their interpretation and use.

Synthesizer. A device that can generate a number of controlled frequencies.

System. A combination of sets, units, assemblies, sub-assemblies, and parts joined together to form a specific operational function or several functions.

System Noise. The output from a powered system with no input applied.