Radio annual and television yearbook (1948)

TELEVISION TALK HEAVISIDE LAYER — The ionosphere. A region of ionized air some fifty miles above the surface of the earth. Its lower boundary acts as a reflective surface or "mirror" for radio waves. Rapid changes in the height of this lower boundary and its contour causes much of the radio interference and fading. HETERODYNING — The process of changing frequency by combining the received signals with the output of an oscillator tube in the receiver. HORIZONTAL CENTERING— The position of the picture with respect to the axis of the cathode rav tube. This is accomplished by a control on the receiver. HORIZONTAL HOLD CONTROL— A control on the receiver for adjusting the number of lines per second to correspond with that of the transmitter. I ICONOSCOPE — A designation used by RCA for a particular type of cathode ray tube developed for the purpose of picking up the scenes to be televised. It is the essential part of a studio camera. IMAGE DISSECTOR — A television camera tube developed by P. T. Farnsworth in which the photoelectrons are moved past pickup aperture by deflection circuits. IMPEDANCE — A combination of electrical resistance and reactance, analogous to mechanical friction and inertia. INTEGRATING CIRCUITS— Circmts used to add up the energy of a number of repeated pulses. These circuits are used in the receiver for synchronization. INTERFERENCE — Random electrical signals which cause noise in the audio system and disrupt the picture in television. This includes automobile-ignition impulses, some diathermy apparatus, neon signs, FM and short wave stations, etc. INTERLACING — A system whereby the odd numbered lines and the even numbered lines of a picture are sent as two separate fields and superimposed to create one frame or complete picture. ION SPOT — A discoloration on the center of the screen of a cathode ray tube caused by heavy negative ions striking it. K KERR CELL — A chemical solution which changes its light transmission characteristics when electric fields are applied to the solution. An early form of a television reproducer system no longer used. KEYSTONE EFFECT— A distorted field or background noticed in some cases with television pictures, where the opposite edges are not parallel. KINESCOPE — A name applied to the cathode ray tubes used in the television receivers built by RCA. L LENS — A radial field (electrostatic or magnetic) applied concentric with a cathode ray to concentrate the diverging electrons into a single slender beam, is called a lens. LINE — The path covered by the moving electron spot. The intensity of the spot along this path is altered to create that portion of the picture. In present system 525 lines make up the complete picture. LINEARITY' — A term used to refer to the straightness of a characteristic curve, or a portion of that curve, that shows the relation between two quantities or circuit factors. The uniformity of distribution of a regular pattern on a picture tube. LINE FREQUENCY — The number of lines scanned each second. In any system it is equal to the number of scanning lines per frame, multiplied by the framing frequency. LINE OF SIGHT — A straight, unobstructed path between two points. LIVE TALENT — "On-the-spot" televising of events and people in contrast to transmission of film material. LUMEN — A lumen is a unit of light flux. A foot-candle is equal to the illumination that falls on a screen that is placed one foot away from a standard candlepower. One foot-candle is equal to the lumen per square foot of surface. M MEGACYCLE—A total of one million cycles. MICROPHONE BOOM — The arm which carries the microphone above the area being televised. , ^ , ,-„.^} 1077