Sec.  73.682   TV transmission standards.

   (a) Transmission standards. (1) The width of the television broadcast
   channel shall be 6 MHz.

   (2) The visual carrier frequency shall be nominally 1.25 MHz above the lower
   boundary of the channel.

   (3) The aural center frequency shall be 4.5 MHz higher than the visual
   carrier frequency.

   (4) The visual transmission amplitude characteristic shall be in accordance
   with the chart designated as Figure 5 of  Sec. 73.699: Provided, however, That
   for stations operating on Channel 15 through 69 and employing a transmitter
   with maximum peak visual power output of 1 kW or less the visual
   transmission amplitude characteristic may be in accordance with the chart
   designated as Figure 5a of  Sec. 73.699.

   (5) The chrominance subcarrier frequency is 63/88 times precisely 5 MHz
   (3.57954545 . . . MHz). The tolerance is  ±10 Hz and the rate of frequency
   drift must not exceed 0.1 Hz per second (cycles per second squared).

   (6) For monochrome and color transmissions the number of scanning lines per
   frame shall be 525, interlaced two to one in successive fields. The
   horizontal scanning frequency shall be 2/455 times the chrominance
   subcarrier frequency; this corresponds nominally to 15,750 Hz with an actual
   value of 15,734.264  ±0.044 Hz). The vertical scanning frequency is 2/525
   times the horizontal scanning frequency; this corresponds nominally to 60 Hz
   (the actual value is 59.94 Hz). For monochrome transmissions only, the
   nominal values of line and field frequencies may be used.

   (7) The aspect ratio of the transmitted television picture shall be 4 units
   horizontally to 3 units vertically.

   (8) During active scanning intervals, the scene shall be scanned from left
   to right horizontally and from top to bottom vertically, at uniform
   velocities.

   (9) A carrier shall be modulated within a single television channel for both
   picture and synchronizing signals. The two signals comprise different
   modulation ranges in amplitude in accordance with the following:

   (i) Monochrome transmissions shall comply with synchronizing waveform
   specifications in Figure 7 of  Sec. 73.699.

   (ii) Color transmissions shall comply with the synchronizing waveform
   specifications in Figure 6 of  Sec. 73.699.

   (iii) All stations operating on Channels 2 through 14 and those stations
   operating on Channels 15 through 69 licensed for a peak visual transmitter
   output power greater than one kW shall comply with the picture transmission
   amplitude characteristics shown in Figure 5 of  Sec. 73.699.

   (iv) Stations operating on Channels 15 through 69 licensed for a peak visual
   transmitter output power of one kW or less shall comply with the picture
   transmission amplitude characteristic shown in Figure 5 or 5a of  Sec. 73.699.

   (10) A decrease in initial light intensity shall cause an increase in
   radiated power (negative transmission).

   (11) The reference black level shall be represented by a definite carrier
   level, independent of light and shade in the picture.

   (12) The blanking level shall be transmitted at 75 ±2.5 percent of the peak
   carrier level.

   (13) The reference white level of the luminance signal shall be 12.5 ±2.5
   percent of the peak carrier level.

   (14) It shall be standard to employ horizontal polarization. However,
   circular or elliptical polarization may be employed if desired, in which
   case clockwise (right hand) rotation, as defined in the IEEE Standard
   Definition 42A65–3E2, and transmission of the horizontal and vertical
   components in time and space quadrature shall be used. For either
   omnidirectional or directional antennas the licensed effective radiated
   power of the vertically polarized component may not exceed the licensed
   effective radiated power of the horizontally polarized component. For
   directional antennas, the maximum effective radiated power of the vertically
   polarized component shall not exceed the maximum effective radiated power of
   the horizontally polarized component in any specified horizontal or vertical
   direction.

   (15) The effective radiated power of the aural transmitter must not exceed
   22% of the peak radiated power of the visual transmitter.

   (16) The peak-to-peak variation of transmitter output within one frame of
   video signal due to all causes, including hum, noise, and low-frequency
   response, measured at both scanning synchronizing peak and blanking level,
   shall not exceed 5 percent of the average scanning synchronizing peak signal
   amplitude. This provision is subject to change but is considered the best
   practice under the present state of the art. It will not be enforced pending
   a further determination thereof.

   (17) The reference black level shall be separated from the blanking level by
   the setup interval, which shall be 7.5 ±2.5 percent of the video range from
   blanking level to the reference white level.

   (18) For monochrome transmission, the transmitter output shall vary in
   substantially inverse logarithmic relation to the brightness of the subject.
   No tolerances are set at this time. This provision is subject to change but
   is considered the best practice under the present state of the art. It will
   not be enforced pending a further determination thereof.

   (19) The color picture signal shall correspond to a luminance component
   transmitted as amplitude modulation of the picture carrier and a
   simultaneous pair of chrominance components transmitted as the amplitude
   modulation sidebands of a pair of suppressed subcarriers in quadrature.

   (20) Equation of complete color signal.

   (i) The color picture signal has the following composition:

   EM=EY′+[EQ′ sin (ωt+33 °)+EI′ cos (ωt+33 °)]

   Where:

   EQ′=0.41(EB′−EY′)+0.48(ER′−EY′).

   EI′=−0.27(EB′−EY′)+0.74(ER′−EY′).

   EY′=0.30ER′+0.59EG′+0.−1EB′.

   For color-difference frequencies below 500 kHz (see (iii) below), the signal
   can be represented by:

   EM=EY′+[(1/1.14)[(1/1.78)(EB′−EY′) sin ωt+(ER′−EY′) cos ωt]]

   (ii) The symbols in paragraph (a)(20)(i) of this section have the following
   significance:

   EM is the total video voltage, corresponding to the scanning of a particular
   picture element, applied to the modulator of the picture transmitter.

   EY′ is the gamma-corrected voltage of the monochrome (black-and-white)
   portion of the color picture signal, corresponding to the given picture
   element.

   Note: Forming of the high frequency portion of the monochrome signal in a
   different manner is permissible and may in fact be desirable in order to
   improve the sharpness on saturated colors.

   EQ′ and EI′ are the amplitudes of two orthogonal components of the
   chrominance signal corresponding respectively to narrow-band and wide-band
   axes.

   ER′, EG′, and EB′ are the gamma-corrected voltages corresponding to red,
   green, and blue signals during the scanning of the given picture element.

   ω is the angular frequency and is 2 times the frequency of the chrominance
   subcarrier.

   The portion of each expression between brackets in (i) represents the
   chrominance subcarrier signal which carries the chrominance information.

   The phase reference in the EM equation in (i) is the phase of the
   burst+180 °, as shown in Figure 8 of  Sec. 73.699. The burst corresponds to
   amplitude modulation of a continuous sine wave.

   (iii) The equivalent bandwidth assigned prior to modulation to the color
   difference signals EQ′ and EI′ are as follows:

   Q-channel bandwidth:

   At 400 kHz less than 2 dB down.

   At 500 kHz less than 6 dB down.

   At 600 kHz at least 6 dB down.

   I-channel bandwidth:

   At 1.3 MHz less than 2 dB down.

   At 3.6 MHz at least 20 dB down.

   (iv) The gamma corrected voltages ER′, EG′, and EB′ are suitable for a color
   picture tube having primary colors with the following chromaticities in the
   CIE system of specification:



                                                             x       y

Red (R).................................................    0.67    0.33
Green (G)...............................................    0.21    0.71
Blue (B)................................................    0.14    0.08


   and having a transfer gradient (gamma exponent) of 2.2 associated with each
   primary color. The voltages ER′, EG′, and EB′ may be respectively of the
   form ER ^1 /γ, EG^1/γ, and EB ^1 /γ although other forms may be used with
   advances in the state of the art.

   Note: At the present state of the art it is considered inadvisable to set a
   tolerance on the value of gamma and correspondingly this portion of the
   specification will not be enforced.

   (v) The radiated chrominance subcarrier shall vanish on the reference white
   of the scene.

   Note: The numerical values of the signal specification assume that this
   condition will be reproduced as CIE Illuminant C (x=0.310, y=0.316).

   (vi) EY′, EQ′, EI′, and the components of these signals shall match each
   other in time to 0.05  µsecs.

   (vii) The angles of the subcarrier measured with respect to the burst phase,
   when reproducing saturated primaries and their complements at 75 percent of
   full amplitude, shall be within  ±10 ° and their amplitudes shall be within
    ±20 percent of the values specified above. The ratios of the measured
   amplitudes of the subcarrier to the luminance signal for the same saturated
   primaries and their complements shall fall between the limits of 0.8 and 1.2
   of the values specified for their ratios. Closer tolerances may prove to be
   practicable and desirable with advance in the art.

   (21) The interval beginning with line 17 and continuing through line 20 of
   the vertical blanking interval of each field may be used for the
   transmission of test signals, cue and control signals, and identification
   signals, subject to the conditions and restrictions set forth below. Test
   signals may include signals designed to check the performance of the overall
   transmission system or its individual components. Cue and control signals
   shall be related to the operation of the TV broadcast station.
   Identification signals may be transmitted to identify the broadcast material
   or its source, and the date and time of its origination. Figures 6 and 7 of
    Sec. 73.699 identify the numbered lines referred to in this paragraph.

   (i) Modulation of the television transmitter by such signals shall be
   confined to the area between the reference white level and the blanking
   level, except where test signals include chrominance subcarrier frequencies,
   in which case positive excursions of chrominance components may exceed
   reference white, and negative excursions may extend into the synchronizing
   area. In no case may the modulation excursions produced by test signals
   extend beyond peak-of-sync, or to zero carrier level.

   (ii) The use of such signals shall not result in significant degradation of
   the program transmission of the television broadcast station, nor produce
   emission outside of the frequency band occupied for normal program
   transmissions.

   (iii) Such signals may not be transmitted during that portion of each line
   devoted to horizontal blanking.

   (iv) Regardless of other provisions of this paragraph, after June 30, 1994,
   Line 19, in each field, may be used only for the transmission of the
   ghost-canceling reference signal described in OET Bulletin No. 68, which is
   available from the FCC Warehouse, 9300 East Hampton Drive, Capitol Heights,
   MD 20743. Notwithstanding the modulation limits contained in paragraph
   (a)(23)(i) of this section, the vertical interval reference signal formerly
   permitted on Line 19 and described in Figure 16 of  Sec. 73.699, may be
   transmitted on any of lines 10 through 16 without specific Commission
   authorization, subject to the conditions contained in paragraphs (a)(21)(ii)
   and (a)(22)(ii) of this section.

   (22)(i) Line 21, in each field, may be used for the transmission of a
   program-related data signal which, when decoded, provides a visual depiction
   of information simultaneously being presented on the aural channel
   (captions). Line 21, field 2 may be used for transmission of a
   program-related data signal which, when decoded, identifies a rating level
   associated with the current program. Such data signals shall conform to the
   format described in figure 17 of  Sec. 73.699 of this chapter, and may be
   transmitted during all periods of regular operation. On a space available
   basis, line 21 field 2 may also be used for text-mode data and extended data
   service information.

   Note: The signals on Fields 1 and 2 shall be distinct data streams, for
   example, to supply captions in different languages or at different reading
   levels.

   (ii) At times when Line 21 is not being used to transmit a program related
   data signal, data signals which are not program related may be transmitted,
   Provided: the same data format is used and the information to be displayed
   is of a broadcast nature.

   (iii) The use of Line 21 for transmission of other data signals conforming
   to other formats may be used subject to prior authorization by the
   Commission.

   (iv) The data signal shall cause no significant degradation to any portion
   of the visual signal nor produce emissions outside the authorized television
   channel.

   (v) Transmission of visual emergency messages pursuant to  Sec. 73.1250 shall
   take precedence and shall be cause for interrupting transmission of data
   signals permitted under this paragraph.

   (23) Specific scanning lines in the vertical blanking interval may be used
   for the purpose of transmitting telecommunications signals in accordance
   with  Sec. 73.646, subject to certain conditions:

   (i) Telecommunications may be transmitted on Lines 10–18 and 20, all of
   Field 2 and Field 1. Modulation level shall not exceed 70 IRE on lines 10,
   11, and 12; and, 80 IRE on lines 13–18 and 20.

   (ii) No observable degradation may be caused to any portion of the visual or
   aural signals.

   (iii) Telecommunications signals must not produce emissions outside the
   authorized television channel bandwidth. Digital data pulses must be shaped
   to limit spectral energy to the nominal video baseband.

   (iv) Transmission of emergency visual messages pursuant to  Sec. 73.1250 must
   take precedence over, and shall be cause for interrupting, a service such as
   teletext that provides a visual depiction of information simultaneously
   transmitted on the aural channel.

   (v) A reference pulse for a decoder associated adaptive equalizer filter
   designed to improve the decoding of telecommunications signals may be
   inserted on any portion of the vertical blanking interval authorized for
   data service, in accordance with the signal levels set forth in paragraph
   (a)(23)(i) of this section.

   (vi) All lines authorized for telecommunications transmissions may be used
   for other purposes upon prior approval by the Commission.

   (24) Licensees and permittees of TV broadcast and low power TV stations may
   insert non-video data into the active video portion of their TV
   transmission, subject to certain conditions:

   (i) The active video portion of the visual signal begins with line 22 and
   continues through the end of each field, except it does not include that
   portion of each line devoted to horizontal blanking. Figures 6 and 7 of
    Sec. 73.699 identify the numbered line referred to in this paragraph;

   (ii) Inserted non-video data may be used for the purpose of transmitting a
   telecommunications service in accordance with  Sec. 73.646. In addition to a
   telecommunications service, non-video data can be used to enhance the
   station's broadcast program service or for purposes related to station
   operations. Signals relating to the operation of TV stations include, but
   are not limited to program or source identification, relay of broadcast
   materials to other stations, remote cueing and order messages, and control
   and telemetry signals for the transmitting system; and

   (iii) A station may only use systems for inserting non-video information
   that have been approved in advance by the Commission. The criteria for
   advance approval of systems are as follows:

   (A) The use of such signals shall not result in significant degradation to
   any portion of the visual, aural, or program-related data signals of the
   television broadcast station;

   (B) No increase in width of the television broadcast channel (6 MHz) is
   permitted. Emissions outside the authorized television channel must not
   exceed the limitations given in  Sec. 73.687(e). Interference to reception of
   television service either of co-channel or adjacent channel stations must
   not increase over that resulting from the transmission of programming
   without inserted data; and

   (C) Where required, system receiving or decoding devices must meet the TV
   interface device provisions of Part 15, Subpart H of this chapter.

   (iv) No protection from interference of any kind will be afforded to
   reception of inserted non-video data.

   (v) Upon request by an authorized representative of the Commission, the
   licensee of a TV station transmitting encoded programming must make
   available a receiving decoder to the Commission to carry out its regulatory
   responsibilities.

   (b) Subscription TV technical systems. The FCC may specify, as part of the
   advance approval of the technical system for transmitting encoded
   subscription programming, deviations from the power determination
   procedures, operating power levels, aural or video baseband signals,
   modulation levels or other characteristics of the transmitted signal as
   otherwise specified in this Subpart. Any decision to approve such operating
   deviations shall be solely at the discretion of the FCC.

   (c) TV multiplex subcarrier/stereophonic aural transmission standards.

   (1) The modulating signal for the main channel shall consist of the sum of
   the stereophonic (biphonic, quadraphonic, etc.) input signals.

   (2) The instantaneous frequency of the baseband stereophonic subcarrier must
   at all times be within the range 15 kHz to 120 kHz. Either amplitude or
   frequency modulation of the stereophonic subcarrier may be used.

   (3) One or more pilot subcarriers between 16 kHz and 120 kHz may be used to
   switch a TV receiver between the stereophonic and monophonic reception modes
   or to activate a stereophonic audio indicator light, and one or more
   subcarriers between 15 kHz and 120 kHz may be used for any other authorized
   purpose; except that stations employing the BTSC system of stereophonic
   sound transmission and audio processing may transmit a pilot subcarrier at
   15,734 Hz,  ±2 Hz. Other methods of multiplex subcarrier or stereophonic
   aural transmission systems must limit energy at 15,734 Hz,  ±20 Hz, to no
   more than  ±0.125 kHz aural carrier deviation.

   (4) Aural baseband information above 120 kHz must be attenuated 40 dB
   referenced to 25 kHz main channel deviation of the aural carrier.

   (5) For required transmitter performance, all of the requirements of
    Sec. 73.687(b) shall apply to the main channel, with the transmitter in the
   multiplex subcarrier or stereophonic aural mode.

   (6) For electrical performance standards of the transmitter, the
   requirements of  Sec. 73.687(b) apply to the main channel.

   (7) Multiplex subcarrier or stereophonic aural transmission systems must be
   capable of producing and must not exceed  ±25 kHz main channel deviation of
   the aural carrier.

   (8) The arithmetic sum of non-multiphonic baseband signals between 15 kHz
   and 120 kHz must not exceed  ±50 kHz deviation of the aural carrier.

   (9) Total modulation of the aural carrier must not exceed  ±75 kHz.

   (d) Digital broadcast television transmission standard. Effective February
   1, 2005, transmission of digital broadcast television (DTV) signals shall
   comply with the standards for such transmissions set forth in ATSC A/52:
   “ATSC Standard Digital Audio Compression (AC–3)� (incorporated by reference,
   see  Sec. 73.8000), ATSC Doc. A/53B, Revision B with Amendment 1 and Amendment 2:
   “ATSC Digital Television Standard,� except for Section 5.1.2 (“Compression
   format constraints�) of Annex A (“Video Systems Characteristics�) and the
   phrase “see Table 3� in Section 5.1.1. Table 2 and Section 5.1.2 Table 4
   (incorporated by reference, see  Sec. 73.8000), and ATSC A/65B: “ATSC Program and
   System Information Protocol for Terrestrial Broadcast and Cable,� (Revision
   B) 2003 (incorporated by reference, see  Sec. 73.8000). Although not incorporated
   by reference, licensees may also consult ATSC Doc. A/54, Guide to Use of the
   ATSC Digital Television Standard, (October 4, 1995), and ATSC Doc. A/69,
   Recommended Practice PSIP Implementation Guidelines for Broadcasters (June
   25, 2002)

   (Secs. 4, 5, 303, 48 Stat., as amended, 1066, 1068, 1082 (47 U.S.C. 154,
   155, 303))

   [ 28 FR 13660 , Dec. 14, 1963]

   Editorial Note:   For Federal Register citations affecting  Sec. 73.682, see the
   List of CFR Sections Affected, which appears in the Finding Aids section of
   the printed volume and on GPO Access.