Federal Communications Commission § 73.681 an indication of the age group for Aspect ratio. The ratio of picture which the program is intended. width to picture height as transmitted. Aural center frequency. (1) The aver- [61 FR 43998, Aug. 27, 1996] age frequency of the emitted wave EFFECTIVE DATE NOTE: At 61 FR 43998, Aug. when modulated by a sinusoidal signal; 27, 1996, § 73.673 was added, effective either (2) the frequency of the emitted wave Jan. 2, 1997 or after approval has been given without modulation. by the Office of Management and Budget, Aural transmitter. The radio equip- whichever comes later. ment for the transmission of the aural § 73.681 Definitions. signal only. BTSC. Broadcast Television systems Amplitude modulation (AM). A system committee recommendation for multi- of modulation in which the envelope of channel television sound transmission the transmitted wave contains a com- and audio processing as defined in FCC ponent similar to the wave form of the Bulletin OET 60. signal to be transmitted. Baseband. Aural transmitter input Antenna electrical beam tilt. The shap- signals between 0 and 120 kHz. ing of the radiation pattern in the ver- Blanking level. The level of the signal tical plane of a transmitting antenna during the blanking interval, except by electrical means so that maximum the interval during the scanning syn- radiation occurs at an angle below the chronizing pulse and the chrominance horizontal plane. subcarrier synchronizing burst. Antenna height above average terrain. Chrominance. The colorimetric dif- The average of the antenna heights ference between any color and a ref- above the terrain from approximately erence color of equal luminance, the 3.2 (2 miles) to 16.1 kilometers (10 reference color having a specific chro- miles) from the antenna for the eight maticity. directions spaced evenly for each 45 de- Chrominance subcarrier. The carrier grees of azimuth starting with True which is modulated by the chro- North. (In general, a different antenna minance information. height will be determined in each di- Color transmission. The transmission rection from the antenna. The average of color television signals which can be of these various heights is considered reproduced with different values of the antenna height above the average hue, saturation, and luminance. terrain. In some cases less than 8 direc- Effective radiated power. The product tions may be used. See § 73.684(d)). of the antenna input power and the an- Where circular or elliptical polariza- tenna power gain. This product should tion is employed, the antenna height be expressed in kW and in dB above 1 above average terrain shall be based kW (dBk). (If specified for a particular upon the height of the radiation center direction, effective radiated power is of the antenna which transmits the based on the antenna power gain in horizontal component of radiation. that direction only. The licensed effec- Antenna mechanical beam tilt. The in- tive radiated power is based on the tentional installation of a transmitting maximum antenna power gain. When a antenna so that its axis is not vertical, station is authorized to use a direc- in order to change the normal angle of tional antenna or an antenna beam maximum radiation in the vertical tilt, the direction of the maximum ef- plane. fective radiated power will be speci- Antenna power gain. The square of the fied.) Where circular or elliptical polar- ratio of the root-mean-square free ization is employed, the term effective space field strength produced at 1 kilo- radiated power is applied separately to meter in the horizontal plane, in the horizontally and vertically polar- millivolts per meter for one kW an- ized components of radiation. For as- tenna input power to 221.4 mV/m. This signment purposes, only the effective ratio should be expressed in decibels radiated power authorized for the hori- (dB). (If specified for a particular direc- zontally polarized component will be tion, antenna power gain is based on considered. the field strength in that direction Equivalent isotropically radiated power only.) (EIRP). The term ``equivalent 185 VerDate 27-NOV-96 13:52 Dec 26, 1996 Jkt 167185 PO 00000 Frm 00185 Fmt 8010 Sfmt 8010 E:\CFR\167185.010 CHICK1 § 73.681 47 CFR Ch. I (10±1±96 Edition) isotropically radiated power'' (also standard scale to the conventional measure known as ``effective radiated power of modulation is as follows: above isotropic'') means the product of IRE stand- Modulation the antenna input power and the an- Level ard scale percentage tenna gain in a given direction relative (units) to an isotropic antenna. Zero carrier .................................... 120 0 Field. Scanning through the picture Reference white ............................. 100 12.5 Blanking ......................................... 0 75 area once in the chosen scanning pat- Synchronizing peaks (maximum tern. In the line interlaced scanning carrier level) ............................... ´40 100 pattern of two to one, the scanning of the alternate lines of the picture area Luminance. Luminous flux emitted, once. reflected, or transmitted per unit solid Frame. Scanning all of the picture angle per unit projected area of the area once. In the line interlaced scan- source. ning pattern of two to one, a frame Main channel. The band of fre- consists of two fields. quencies from 50 to 15,000 Hertz which Free space field strength. The field frequency modulate the main aural strength that would exist at a point in carrier. the absence of waves reflected from the Monochrome transmission. The trans- earth or other reflecting objects. mission of television signals which can Frequency departure. The amount of be reproduced in gradations of a single variation of a carrier frequency or cen- color only. ter frequency from its assigned value. Multichannel Television Sound (MTS). Frequency deviation. The peak dif- Any system of aural transmission that ference between the instantaneous fre- utilizes aural baseband operation be- quency of the modulated wave and the tween 15 kHz and 120 kHz to convey in- carrier frequency. formation or that encodes digital infor- Frequency modulation (FM). A system mation in the video portion of the tele- of modulation where the instantaneous vision signal that is intended to be de- radio frequency varies in proportion to coded as audio information. the instantaneous amplitude of the Multiplex Transmission (Aural). A sub- modulating signal (amplitude of modu- channel added to the regular aural car- lating signal to be measured after pre- rier of a television broadcast station by emphasis, if used) and the instanta- means of frequency modulated subcar- neous radio frequency is independent of riers. Where a de- the frequency of the modulating signal. Negative transmission. crease in initial light intensity causes Frequency swing. The peak difference an increase in the transmitted power. between the maximum and the mini- Peak power. The power over a radio mum values of the instantaneous fre- frequency cycle corresponding in am- quency of the carrier wave during mod- plitude to synchronizing peaks. ulation. Percentage modulation. As applied to Interlaced scanning. A scanning proc- frequency modulation, the ratio of the ess in which successively scanned lines actual frequency deviation to the fre- are spaced an integral number of line quency deviation defined as 100% mod- widths, and in which the adjacent lines ulation expressed in percentage. For are scanned during successive cycles of the aural transmitter of TV broadcast the field frequency. stations, a frequency deviation of ±25 IRE standard scale. A linear scale for kHz is defined as 100% modulation. measuring, in IRE units, the relative Pilot subcarrier. A subcarrier used in amplitudes of the components of a tele- the reception of TV stereophonic aural vision signal from a zero reference at or other subchannel broadcasts. blanking level, with picture informa- Polarization. The direction of the tion falling in the positive, and syn- electric field as radiated from the chronizing information in the negative transmitting antenna. domain. Program related data signal. A signal, NOTE: When a carrier is amplitude modu- consisting of a series of pulses rep- lated by a television signal in accordance resenting data, which is transmitted si- with § 73.682, the relationship of the IRE multaneously with and directly related 186 VerDate 27-NOV-96 13:52 Dec 26, 1996 Jkt 167185 PO 00000 Frm 00186 Fmt 8010 Sfmt 8010 E:\CFR\167185.010 CHICK1 Federal Communications Commission § 73.682 to the accompanying television pro- Visual carrier frequency. The fre- gram. quency of the carrier which is modu- Reference black level. The level cor- lated by the picture information. responding to the specified maximum Visual transmitter. The radio equip- excursion of the luminance signal in ment for the transmission of the visual the black direction. signal only. Reference white level of the luminance Visual transmitter power. The peak signal. The level corresponding to the power output when transmitting a specified maximum excursion of the lu- standard television signal. minance signal in the white direction. [28 FR 13660, Dec. 14, 1963, as amended at 35 Scanning. The process of analyzing FR 5692, Apr. 8, 1970; 36 FR 5505, Mar. 24, 1971; successively, according to a predeter- 36 FR 17429, Aug. 31, 1971; 41 FR 56325, Dec. 28, mined method, the light values of pic- 1976; 42 FR 20823, Apr. 22, 1977; 44 FR 36039, ture elements constituting the total June 20, 1979; 47 FR 35990, Aug. 18, 1982; 49 FR 18106, Apr. 27, 1984; 49 FR 38131, Sept. 27, 1984; picture area. 49 FR 50048, Dec. 26, 1984; 50 FR 23699, June 5, Scanning line. A single continuous 1985; 51 FR 12616, Apr. 14, 1986; 56 FR 49707, narrow strip of the picture area con- Oct. 1, 1991; 58 FR 44951, Aug. 25, 1993] taining highlights, shadows, and half- tones, determined by the process of § 73.682 TV transmission standards.