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A ABSORPTION TRAP--A parallel-tuned circuit coupled either magnetically or capacitively, to absorb and attenuate interfering signals. ACCOMPANYING AUDIO (SOUND) CHANNEL. The RF carrier frequency which supplies the sound to accompany the picture. Also known as Co-channel Sound Frequency. ACTIVE LINES--The lines which produce the picture as distinguished from the lines occurring during blanking (horizontal and vertical retrace lines). ADJACENT AUDIO (SOUND) CHANNEL--The RF carrier frequency which carries the sound modulation associated with the next lower frequency television channel. ALUMINIZED SCREEN PICTURE TUBE--A cathode-ray picture tube in which a thin layer of aluminum has been deposited on the back of the fluorescent surface to improve the brilliance of the image and prevent ion spot formation. AMPLITUDE MODULATION (AM)--A method of modulating an RF carrier in which the instantaneous amplitude of the carrier is proportional to the instantaneous value of the modulating voltage. AMPLITUDE SEPARATION--The method of sorting part of a voltage wave (particularly the sync pulses of the video signal) from the rest of the wave by differences in amplitude. This is usually accomplished by employing a biased clipper. AQUADAG--A colloidal solution of graphite in water, used to produce a conductive coating on the surface of the glass envelope of cathode-ray picture tubes. This is done internally to collect secondary electrons emitted by the fluorescent screen and externally (in some types) to utilize the tube as a final capacitor of the high voltage filter circuit. ARRAY--A combination or arrangement of antenna elements to produce a desired directional pattern or increase in signal pick up as compared with a half wave dipole. ASPECT RATIO--The numerical ratio of the picture width to its height. The television and motion picture standard is 4/3. ASSYMETRIC SIDE-BAND TRANSMISSION--(See Vestigial Side Band Transmission.) AUDIO CHANNEL--(See Accompanying Audio Channel.) AUTOMATIC GAIN CONTROL (A.G.C.)--A method of automatically regulating the overall amplification (gain) of a television receiver to produce constant output (contrast of the picture) for varying input signals. AUTOMATIC CONTRAST CONTROL--(See Automatic Gain Control.) AUTOMATIC PHASE CONTROL--A method of automatically holding the frequency and phase of the horizontal scanning oscillator in step with the repetition rate and phase of the horizontal sync pulses. B BACKGROUND--In television this refers to the average illumination of the scene and is represented by the DC component of the video signal. (See DC Video Component.) "BACK PORCH"--The portion of the synchronizing signal (at blanking or black level) which follows the horizontal sync pulse and precedes the start of the next horizontal active line. (3.81 microseconds in duration for the standard R. M. A. signal.) BANDWIDTH--The difference in frequency between the highest and lowest frequencies involved. A television channel has a bandwidth of 6 megacycles. BEAM--In television this refers to a stream of electrons moving in a parallel path. BEAM CURRENT--The electrical current comprised of a beam of electrons. BEAM RELAXOR--A type of sawtooth scanning oscillator circuit which generates the current wave required for magnetic deflection in a single beam-power pentode without employing subsequent amplification. "BI-DIRECTIONAL"--Refers to the shape of the reception pat tern of an antenna which responds equally well to stations located 180 degr. apart with respect to the receiver. "BLACKER-THAN-BLACK"--Also "Infra-Black". That portion of the video modulating voltage of the transmitter of greater amplitude than the black level (from 75% to 100% of maximum signal). This region is occupied by the synchronizing pulses. BLACK LEVEL--The amplitude of the video modulating wave at which the team of the picture tube is extinguished (becomes black), to blank retrace of the beam. This level is established at 75% of the maximum of the signal. BLANKING PULSES--The portion of the video modulating signal during which the beam of the picture tube is extinguished (at or above 75% of maximum signal.) (See Black Level.) BLOCKING OSCILLATOR--A type of relaxation oscillator circuit, for the generation of sawtooth waves, employing an iron core feedback transformer and a long time constant grid capacitor-resistor network. BLOOMING--The phenomenon of defocusing of regions of the picture due to excessive brilliance. The spot size is enlarged to halation (spreading of light at the fluorescent screen). "BOOSTER"--A separate radio frequency amplifier connected between the antenna and the television receiver to amplify weak signals. BRIGHTNESS CONTROL--The adjustment means of a television receiver whereby the operating point of the picture tube is set to prevent the appearance of the beam retrace. C CAMERA TUBE--The device employed at the television transmitter to change the light variations of the scene into a video modulation. Examples: Iconoscope, Image Orthicon, Image Dissector and Monoscope. CATHODE FOLLOWER--A vacuum tube circuit in which the input signal is applied between control grid and ground, while the output is taken between cathode and ground. The plate is by passed to ground. A cathode follower exhibits high input impedance and low output impedance. CATHODE INPUT--(See Grounded Grid Amplifier.) CENTERING CONTROL--Adjustment means for controlling the position of the raster on the picture tube screen. (See Horizontal Centering Control, and Vertical Centering Control.) CHANNEL--The band of frequencies assigned for the trans mission of the television signal. CHARACTERISTIC IMPEDANCE--The ratio of the voltage to the current at every point on an RF transmission line. This holds only when the line is properly terminated and no standing waves are present. CLAMPING CIRCUIT--See also DC Restoration. A circuit which maintains one extreme of a voltage wave at a predetermined DC level. CLIPPING CIRCUIT--A vacuum tube circuit arranged to operate under conditions which remove one or both extremities of an impressed voltage wave. This produces a flat topped output. Employed in sync pulse shaping. COAXIAL CABLE (COAX)--A high frequency transmission cable consisting of a central inner conductor and a cylindrical shaped surrounding conductor, the conductors being separated by an insulator. Often employed as a television antenna lead-in. COMPOSITE SIGNAL--A television signal whose waveform is composed of video modulation, blanking pedestal and synchronizing pulses. In the R. M.A. standard the blanking pedestal occurs at 75% of maximum signal and the sync pulses occupy the remaining 25%. CONTRAST--The range of light to dark values of the image, proportional to the voltage swing at the picture tube input. CONTRAST CONTROL--The adjustment means of a television receiver whereby the input voltage swing to the picture tube input is set to produce the most acceptable image contrast. CRITICAL VIEWING DISTANCE--The ratio of the distance of the observer to the height of the picture, at which the line structure just disappears (about 5 to 1, with present standards). D DC REINSERTION--The combining of the DC component of the video signal (lost in capacitance-coupled amplifiers) with the AC component to re-establish the average light value of the reproduced picture. DC VIDEO COMPONENT--The part of the video signal caused by the average steady background illumination of the scene being televised. DAMPING TUBE--A vacuum tube (diode or triode) used to momentarily short circuit the stored energy in a deflecting coil system and prevent transient oscillation. DEFINITION--The sharpness of fine detail in the reproduced picture. DEFLECTION--The process whereby the electron beam of a picture tube is deviated from its axial path (either electrostatically or electromagnetically) to produce the scanning raster. DEFLECTION YOKE--An assembly consisting of the horizontal and vertical deflection coils of a magnetically deflected TV set. DETAIL--The least perceptible elements or areas of an image which can be recognized as different from one another. DIATHERMY--An interfering signal caused by certain types of medical apparatus. Contains strong 60 cycle modulation and produces a "herring-bone" pattern on the picture. DIFFERENTIATING CIRCUIT--A combination of circuit elements which produce an output pulse proportional to the rate of change of the input signal. DIPOLE--An antenna whose length is approximately one half of the electromagnetic wavelength to which it is resonant. It is usually divided in the middle for connection too the transmission line. DIRECTOR--A dipole placed in front of a dipole antenna element (toward the transmitter). Its function is to increase the pick-up and obtain a directional pattern. DISCHARGE TUBE--A vacuum tube (usually a triode, normally biased to be non-conductive which is arranged to discharge a condenser when triggered by a positive voltage pulse. DISCRIMINATOR--An FM detector circuit using a pair of diodes. The audio output is proportional to the frequency deviation. DISSECTOR--A camera tube in which an electron image is moved across the aperture of an electron multiplier. E ECHO--A delayed signal due to reflection. This may refer either to the television carrier (ghost signals) or to effects in the video amplifier. ELECTRON FOCUS--The reduction in size of the electron beam in a picture tube by variation of the electrostatic field. ELECTROMAGNETIC DEFLECTION COIL--A circular coil placed around the neck of a picture tube to cause deflection of the electron beam. ELECTRON--The elementary electrical charge of negative sign or polarity (1.6x10^-19 coulombs). ELECTRON GUN--An arrangement of cylindrical electrodes and baffles with apertures which produce a small beam of electrons. ELECTRON MULTIPLIER--An electron tube in which a number of electrodes are arranged in cascade. Each electrode delivers to the next a greater number of electrons than it receives. The increase is due to secondary emission. ELECTRON SCANNING--The deflection of an electron beam to form a regular pattern or raster. ELECTROSTATIC FIELD -A strain in space which exerts a force on an electrical charge (electron) within its region of in fluence. ELECTROSTATIC SCANNING--The deflection of an electron beam, to form a raster, by means of an electrostatic field. EQUALIZING PULSES--A series of pulses (usually six in number), occurring at twice line frequency, which precede and follow the serrated vertical synchronizing pulse. The purpose of these pulses is to cause vertical retrace to occur at the correct instant for proper interlace. F FIELD--One complete scanning operation from top to bottom of the picture including retrace to the top again. In the R. M. A. standard this requires 1/60th of a second and occurs twice per frame. FIELD FREQUENCY--The number of fields transmitted per second (60 in the standard R. M. A. system). FIELD FREQUENCY SYNCHRONIZING IMPULSE--(See Vertical Blanking Impulse.) FIELD PERIOD--The time required to transmit one field (reciprocal of the field frequency) or 1/60th of a second. FLUORESCENT SCREEN--The coating on the inside surface of the picture tube (a phosphor which emits light under the impact of the electron beam). FLYBACK--The return of the electron beam after tracing a horizontal line. (See retrace.) FLYWHEEL SYNC--A method of horizontal synchronization in which the control of scanning is determined by the average timing of the sync pulses rather than by each individual pulse as in triggered sync. FOCUSING CONTROL--The adjustment means of a television receiver whereby the electron beam is brought to the smallest possible spot size on the fluorescent screen. FOLDED DIPOLE--A dipole antenna which consists of two half wave dipoles arranged parallel to one another and with their extremities connected together. One of the dipoles is open at its center point for connection to the transmission line. FRAME--The complete single picture contained in an image. In the standard double interlace system, a frame consists of two fields and has a repetition rate of 30 per second. FRAME FREQUENCY--The number of times per second the picture is completely scanned--the standard is 30 per second. "FRONT PORCH"--The portion of the synchronizing signal (at blanking or black level) which precedes the horizontal sync pulse and occurs at the end of each active horizontal line (1.27 micro seconds in duration for the standard R. M. A. signal). FRONT-TO-BACK RATIO--The ratio of the sensitivity of an antenna for signals arriving from the front (desired direction) to the sensitivity for signals arriving from the back, 180 degrees from the front. G GAMMA--The ratio of the contrast of any two elements of the picture to the original contrast of these same elements in the scene being televised. GHOST IMAGE--A second or echo image superimposed on the reproduced picture due to a reflected and delayed carrier wave. GRID LIMITING--The use of grid current bias derived from the signal through a large series grid resistor to cause plate current cut-off and consequent leveling of the output wave for all input signals above a critical value. GROUNDED GRID AMPLIFIER--A vacuum tube circuit in which the input signal is applied between a grounded grid and the cathode. The, grid thus acts as a shield between the input circuit (cathode-to-ground) and the output circuit (connected between plate and ground). H HALATION--A halo immediately surrounding a point of high brilliance on the fluorescent screen. This may be due to light scattering in the phosphor or multiple reflections between front and back surfaces of the glass. HALF WAVE DIPOLE OR "DOUBLET"--(See Dipole.) HEIGHT CONTROL--The adjustment means of a television receiver which controls the vertical scanning amplitude and hence the height of the picture. HOLD CONTROL--The adjustment means of a television receiver which permits control of the frequency of a scanning oscillator (horizontal or vertical) to produce coincidence with the synchronizing rate of the transmitted signal. HORIZONTAL BLANKING--The process of cutting off the electron beam during retrace between successive active horizontal lines. HORIZONTAL BLANKING IMPULSE--The rectangular shaped pedestal of the composite television signal which occurs between active horizontal lines. This causes the beam current of the picture tube to be cut off during retrace. HORIZONTAL CENTERING CONTROL--The adjustment means of a television receiver whereby the image may be moved in the horizontal direction. HORIZONTAL DISCHARGE TUBE--A vacuum tube in the horizontal deflection circuit which is used to discharge a capacitor to form the sawtooth scanning wave. (See Discharge Tube.) HORIZONTAL DRIVE CONTROL--The adjustment means of an electromagnetically deflected television receiver which adjusts the ratio of pulse to linear portion of the scanning current wave. HORIZONTAL FLYBACK--(See Horizontal Retrace.) HORIZONTAL HOLD CONTROL--(See Hold Control.) HORIZONTAL REPETITION RATE--The number of horizontal lines per second (15,750 cycles in the R. M. A. standard system). HORIZONTAL RESOLUTION--The number of picture elements, in the horizontal direction, which can be distinguished from each other. HORIZONTAL RETRACE--(See Retrace.) HORIZONTAL SCANNING FREQUENCY--(See Horizontal Re petition Rate.) HORIZONTAL SYNC DISCRIMINATOR--A circuit employed in the flywheel method of synchronization to compare the phase of the horizontal sync pulses with that of the horizontal scanning oscillator. The output of the discriminator controls the frequency and phase of the oscillator by means of a reactance tube. HORIZONTAL SYNC IMPULSE--The rectangular shaped pulses which occur, above pedestal level, between each active horizontal line. These pulses are employed to hold horizontal scanning of the receiver in coincidence with that of the transmitter. HUM-BAR--A dark band extending across the picture caused by excessive 60 cycle hum (or harmonics thereof) in the signal applied to the input of the picture tube. ICONOOCOPE--A television camera tube in which an optical image on a mosaic of photo-sensitive elements causes charges proportional at each point to the image intensity. Aft electron scanning beam releases these charges in the form of a video signal. IMAGE DISSECTOR--(See Dissector.) IMAGE INTERFERENCE--A spurious response in a television receiver due to signals of a frequency removed from the desired signal by twice the intermediate frequency of the TV set. Usually due to a local FM carrier, or another television carrier. IMAGE ORTHICON--A camera tube combining the orthicon principle with that of the electron multiplier. It possesses a very high value of light sensitivity. "IMPLODE"--The term applied to the bursting of a television picture tube. Due to the high degree of vacuum the glass fragments move inward with terrific force. "INFRA-BLACK"--(See "Blacker-than-Black''.) INTEGRATING CIRCUIT--A combination of circuit elements which produce an output potential which is proportional to the stored-up value of a number of pulses of input signal. INTERCARRIER SOUND--A method of utilizing the 4.5mhz beat between video and sound carriers as an IF frequency for the sound signal of the television receiver. INTERLACE--A method of scanning an image in several successive fields, each of which contains only part of the horizontal line structure, the fields being arranged to fit together so that successive fields supply the lines missed by the preceding fields. In the standard R.M.A. system double interlace is employed. Half the lines (262.5) are scanned in one field and the other half in the next field. The lines of the second field are arranged to fall exactly between the lines of the first. This system over-comes flicker of the picture. INTERLACED SCANNING--A method of scanning the television image to reduce flicker. (See Scanning.) ION--A charged atom. In the picture tube such ions interfere with the operation by producing a dark spot at the center of the fluorescent screen unless deflected away from the screen by an ion trap. ION SPOT--A dark spot on the fluorescent screen of a picture tube caused by bombardment by ions. ION TRAP--An arrangement of picture tube electrodes in combination with an externally applied magnetic field which allows electrons to pass but obstructs the passage of ions·. K KEYSTONE--A trapezoid shape. A television picture with one side shorter than the other is said to have keystone distortion. May be encountered due to faulty adjustment of the optical system of projection television receivers. KEYSTONE DISTORTION--(See Keystone.) L LIMITER--An amplifier stage preceding an FM detector so operated that all input signals above a predetermined minimum drive the stage to cut-off and plate current saturation thus limiting the output signal to a fixed value. Used to remove amplitude modulation. LINE FREQUENCY--(See Horizontal Repetition Rate.) LINE FREQUENCY BLANKING IMPULSE--(See Horizontal Blanking Impulse.) LINE SCANNING FREQUENCY--(See Horizontal Repetition Rate.) LINEARITY--The distribution of picture elements over the image field as determined by the shape of the horizontal and vertical scanning waves. In a linear picture the elements are uniformly and correctly distributed. Any departure from linearity of scanning motion will result in distortion of the picture. LINEARITY CONTROL--The adjustment means of a television receiver employed to correct distortion of the sawtooth voltage or current waves used for deflection. Linearity controls are employed for both horizontal and vertical correction. LINE DOUBLING--Another term applied to Horizontal Equalizing Pulses . M MAGNETIC DEFLECTION--The method of moving the electron beam by means of a magnetic field produced by a coil external to the picture tube. A linear sawtooth motion is produced when the current through the coil has a sawtooth form. MARKER PIP--A frequency index mark employed in cathode-ray oscilloscope alignment of TV sets and used in conjunction with a sweep driven signal generator. The marker pip is produced by coupling a fixed frequency oscillator to the output of the signal generator. MAGNETIC FIELD--The space near a magnet or electromagnet in which a force is exerted upon a moving electron. MONITOR--A cathode-ray picture tube, and its associated circuits, usually connected directly to the video system of the transmitter and used to view the picture being transmitted. MONOOCOPE -A cathode-ray tube used to produce a video signal for testing purposes. A fixed internal test pattern is employed. MOSAIC--The photo-sensitive surface of an iconoscope or orthicon camera tube. It consists of an insulating surface covered with a multitude of photo-sensitive "islands". A collector plate behind the insulator collects the charges on the mosaic when scanned by an electron beam. MULTI-PATH RECEPTION--The reception of a direct wave from the television transmitter accompanied by one or more reflected and delayed waves. (See Ghost Image.) MULTIPLIER--(See Electron Multiplier.) MULTIVIBRATOR--A relaxation oscillator used for the production of sawtooth scanning waves in a television receiver, employing two tubes with the output of each coupled to the input of the other through C-R networks which determine the period of oscillation. N N.T.S.C.--The abbreviation for National Television System Committee. Disbanded since adoption of R.M.A. standards. Now superseded by J. T. A. C. (Joint Technical Advisory Committee). NEGATIVE TRANSMISSION--This refers to the polarity of modulation of the R. M. A. standard television signal. The sync pulses and signals corresponding to black, drive the carrier to maximum modulation, while signals of highest brilliance (white) drive the carrier toward zero modulation. NOISE--In terms of television, noise (a term carried over from sound broadcasting) produced by atmospherics, tube fluctuation effects and man-made interference, causes a salt and pepper, or "snow" pattern on the picture. NON-LINEARITY--The crowding of picture elements in the horizontal direction or crowding of lines at top or bottom due to departure of the scanning action from a linear form. (See Linearity.) O ODD-LINE INTERLACE--Refers to the double interlace system in which there are an odd number of lines per frame and in which, therefore, each field contains a half line. ORTHICON--A camera tube of similar design to the iconoscope but employing a translucent mosaic with a ring collector and using a lower velocity scanning beam. An improved form of iconoscope. P PAIRING--A failure of proper interlace in which the lines of alternate fields do not fall exactly between those of the preceding field. When failure is most pronounced the lines of alternate fields fall on one another and result in separated lines with half of the possible vertical resolution. PEAKING COIL--An inductance employed in a video amplifier to resonate with the circuit capacitance beyond the upper limit of the band and thus compensate for high frequency loss of gain and also to correct the amplifier phase shift. PEDESTAL--The level of the video signal at which blanking of the beam of the picture tube occurs. (See Blanking Pulses and Black Level.) PERSISTENCE OF VISION--A characteristic of the eye and brain whereby the sensation of an image remains after the light causing it has vanished. This effect lasts for approximately an eighth of a second and makes television as well as motion pictures possible. PHASE--A point in the cycle of an alternating current or voltage as compared to the time of zero value (expressed in degrees out of 360, which represents the total cycle). PHASE-DISTORTION--A condition of different phase delays for different video frequencies. This causes distortion of the peak values of the video signal and results in defective contrast and resolution. PHOTO-ELECTRIC--The phenomenon whereby electrons are emitted from certain substances by absorption of light. Employed in camera tube operation. The substance is said to be photo-emissive. PICKUP TUBE--Used synonymously with camera tube. PICTURE ELEMENT--The smallest picture area which can be defined in the process of scanning, transmitting and reproducing the video signal. PICTURE TUBE--A special version of the cathode-ray tube used in television reception for the translation of the video signal to a picture. "PIX"--Television slang abbreviation for picture. POLARIZATION--The direction of the electric field of a radiated wave. The magnetic field is perpendicular to the electric. Television transmission is usually horizontally polarized. PRE-EMPHASIS--The practice of amplifying the high frequency end of the audio spectrum to a greater extent than the low frequencies. Employed in FM transmission of the television sound channel. PULSE--Shortened expression for impulse. PULSE WIDTH--The time duration of the narrow or peaked portion of an impulse wave. Q "Q"--The figure of merit of a capacitor, an inductor or a tuned circuit. It is numerically equal to the ratio of the reactance to the resistance. "QUASI-OPTICAL"--Having properties similar to light waves. Thus the propagation of waves in the television spectrum is said to be "Quasi-optical", i.e., cut off by the horizon. "QUASI-SINGLE SIDEBAND" -- Same as Vestigial Sideband. R RC CIRCUIT--A time determining network of resistors and capacitors in which the time constant is defined as the product of the resistance times the capacitance. R. M. A.--The Radio Manufacturers Association. The technical committees of this association have been instrumental in establishing the television standards now accepted by the Federal Communication Commission. RASTER--The scanned area on the fluorescent screen of the picture tube. The illuminated rectangle composed of all of the horizontal scanning lines. (Visible when the brilliance control is turned up with no signal.) RATIO DETECTOR--An FM detector which inherently discriminates against amplitude modulation. It uses a pair of diodes connected in such a manner that the audio output is proportional to the ratio of the FM voltages applied to the two diodes. REACTANCE TUBE CIRCUIT--A vacuum tube circuit in which a high transconductance tube is so connected that it appears as a reactance (inductive or capacitive) to a circuit across which it is connected. The value of the reactance can be controlled by changing the DC grid bias. Used for A.F.C. REFLECTIONS--In television this refers to the reflected carrier wave from structures and also to the "Ghost Image" on the picture caused by the reflected carrier. REFLECTOR--A half wave dipole placed behind a dipole receiving antenna, to intensify the received signal and improve the shape of the directional antenna pattern. REGISTRY--The superposition of one image on another, as in the formation of an interlaced scanning raster. REINSERTER--Same as DC Restorer. (See DC Reinsertion.) RELAXATION OSCILLATOR--An oscillator which generates periodic waves (usually of a sawtooth form for scanning purposes) in which a sudden excursion of plate current from cut-off to saturation is followed by a relatively long period of quiescence or relaxation. RESOLUTION--This refers to the smallest element of the picture which can be distinguished. It is usually expressed as the number of alternate black and white lines which can be seen in a television test chart. The resolution in the horizontal and vertical directions are expressed separately. RESOLUTION PATTERN--(See Television Test Chart.) RETRACE--The return of the electron beam after horizontal or vertical scan to start a new line or field. RETRACE TIME--The time which elapses during retrace. In the R. M. A. signal this is approximately 7 microseconds for the horizontal retrace and 500 to 750 microseconds for the vertical retrace. RHOMBIC ANTENNA--A diamond shaped arrangement of conductors, each of the same length (rhombus). Joined at 3 corners with a transmission line connected at the open corner. The length of the conductors to be more than a wavelength. Used for fringe or low signal reception. S SAWTOOTH--The descriptive term used for the waveform employed in television scanning. SCANNING--The process of successively analyzing the light values of the picture elements which constitute the entire scene being televised according to a predetermined method. SCANNING GENERATOR--A vacuum tube circuit used to pro duce the sawtooth wave of voltage or current required for transmitter camera tube or receiver picture tube operation. SCANNING LINE--A single active horizontal line of the picture. SCANNING SPOT--The cross section of the electron beam at the fluorescent screen of the picture tube. SCHMIDT SYSTEM--An optical system employed to produce large size projection images. A large hemispherical mirror is employed to project the image formed on a small picture tube onto a translucent screen. Optical distortion is compensated by interposing an aspherical corrector lens in the projection path. SCREEN PERSISTENCE--The property of the fluorescent screen of a picture tube to continue the radiation of light for a short time after the electron beam causing the light spot has passed. SECONDARY ELECTRON--An electron which is knocked out of a metal surface under the bombardment of another electron, called the primary electron. SECONDARY EMISSION--The phenomenon of the production of secondary electrons. (See Secondary Electron.) SEQUENTIAL INTERLACE--A system of interlace in which the lines of one field fall directly alongside the lines of the preceding field. (See Odd Line Interlace.) SESQUI-SIDEBAND TRANSMISSION--The transmission of a carrier modulated by a full sideband and half of the other. (See Vestigial Sideband Transmission.) SERIES PEAKING--The use of an inductance in series with the plate of a video amplifier tube to compensate for loss of high frequency gain and to correct high frequency phase shift. SERRATED PULSES--"Notches" in the long vertical sync pulse which provide a means of keeping the horizontal oscillator in synchronism during the vertical retrace period. SHADOWS--Used synonymously with "Ghost". SHUNT PEAKING--The use of an inductance in a parallel circuit branch of a video amplifier to compensate for the high frequency loss due to the shunt circuit capacitance. It is also used to correct the high frequency phase shift. SINGLE ENDED--This refers to input circuits of television receivers in which one side of the transmission line is connected to the chassis or ground. SINGLE SIDEBAND--A method of radio transmission in which the carrier and only one sideband are radiated. "SMEAR" GHOST--A spurious image caused by a number of multiple reflections or by phase shift in the video amplifier. "SNOW"--Television slang for the effect of random noise on the reproduced picture. (See Noise.) SPURIOUS SIGNAL--Refers either to the effect of reflections or the carrier wave or undesirable shading signals occurring in the camera tube at the transmitter. STACKED ARRAYS--This term is applied to antenna systems in which two or more antenna arrangements are positioned above one another at a critical spacing and connected together with lengths of transmission line. Stacking increases the pickup and Improves the directional pattern. STAGGERED CIRCUITS--Interstage coupling circuits of a video IF amplifier are said to be staggered when they are tuned to different frequencies. Staggered tuning is adopted to obtain broadband response. SURGE IMPEDANCE--Same as Characteristic Impedance. SWEEP--Same as scan. Refers to motion of an electron beam at right angles to its direction. SWEEP VOLTAGE--The voltage applied to the deflection plates of an electrostatically deflected picture tube. SYNC--An abbreviation for synchronization. SYNC CLIPPER--A vacuum tube circuit which Is biased so as to remove the sync signals from the composite video signal. SYNC INVERTER--A vacuum tube circuit which produces a phase shift of the sync pulses of 180 degr. to provide the necessary polarity for control of the scanning oscillator. SYNC LEVELER--(See Sync Limiter.) SYNC LIMITER--A vacuum tube circuit which produces uniform height sync pulses. SYNC SEPARATOR--(See Sync Clipper.) SYNCHROGUIDE--A type of control circuit for horizontal scanning in which sync signal, oscillator voltage pulse and scanning voltage are compared and kept in synchronism. SYNCHRONIZING PULSES--The portions of the transmitted signal which control horizontal and vertical scanning of the receiver. (See Horizontal and Vertical Sync Pulses.) T TEARING--A fault of the synchronizing system in which groups of lines are displaced causing the appearance of a "torn" picture. TELEGENIC--The suitability of a subject or model for televising. TELEVISE--The act of converting a scene or image field into a television signal. TELEVISION TEST CHART--A chart placed before the camera of the transmitter, having geometric patterns which enable the service technician or set user to determine the horizontal and vertical resolution of the receiver. TEST PATTERN--(See Television Test Chart.) TIME CONSTANT--The time required for the voltage or current of an electric circuit to rise to 63% of its final value or to fall to 37% of its Initial value. TIME DELAY--The time which elapses between the start of a modulation wave or impulse at the transmitter and the start of its reproduction on the picture tube screen. TRANSIENT RESPONSE--The manner in which an electrical circuit responds to sudden changes in applied potential. TRANSMISSION LINE--A two-conductor circuit, having uniformly distributed electrical constants, used for transmitting radio frequency signals. TRIGGERING--Starting of action in a circuit, which then continues to function for a predetermined time under its own control. U.H.F. (ULTRA HIGH FREQUENCY) WAVES--The band of frequencies from 300 to 3000 megacycles. Proposed for extension of the present black and white television and for experimental transmission of color television. V V.H.F. (VERY HIGH FREQUENCY) WAVES--The portion of the spectrum employed, at present, for television transmission. The limits are 30 to 300 megacycles. VERTICAL BLANKING--The blanking signals which occur at the end of each vertical field and cause the picture tube to be come dark during vertical retrace. VERTICAL BLANKING IMPULSE--(See Vertical Blanking.) VERTICAL CENTERING CONTROL--The adjustment means of a television receiver whereby the picture can be moved in a vertical direction on the picture tube. VERTICAL HOLD CONTROL--(See Hold Control.) VERTICAL OSCILLATOR--The sawtooth scanning generator which furnishes the required voltage or current wave for vertical scanning. VERTICAL RESOLUTION--The line-structure of the television picture. The number of lines or picture elements which can be resolved in the vertical direction. VERTICAL RETRACE--The return path of the electron beam (blanked out) across the raster from bottom to top at the end of each field. VERTICAL SCANNING--The movement of the beam on the picture tube in the vertical direction. VERTICAL SCANNING GENERATOR--(See Vertical Oscillator.) VERTICAL SYNC PULSES--A series of six pulses (longer in time duration than the horizontal pulses) which occur between each field and are used to synchronize the vertical scanning oscillator. VESTIGIAL SIDEBAND TRANSMISSION--The system of video modulation employed under R. M. A. standards. The carrier is modulated by a complete upper sideband and a vestige (1.25mhz) of the lower sideband. VIDEO (LATIN FOR "ISEE".) --Refers to the frequencies employed for modulation of the carrier by the output of the camera tube. W WEDGE--The convergent, fan shaped pattern of equidistant black and white triangularly shaped lines used on a television test pattern. WIDTH--In television this term may refer to the horizontal dimension of the picture or to the time duration of a pulse (pulse width). WIDTH CONTROL--The adjustment means of a television receiver whereby the horizontal dimension of the picture is adjusted to fill the picture tube. Y "YAGI" ARRAY--An. arrangement of dipole antenna elements employed for television reception in which one element acts as the antenna and the other s as parasitic elements (directors and/ or a reflector) to improve gain and directional reception pattern. |