§ 79.101   Closed caption decoder requirements for analog television
receivers.

   (a)(1) Effective July 1, 1993, all television broadcast receivers with
   picture screens 33 cm (13 in) or larger in diameter shipped in
   interstate commerce, manufactured, assembled, or imported from any
   foreign country into the United States shall comply with the provisions
   of this section.

   Note to paragraph (a)(1): This paragraph places no restriction on the
   shipping or sale of television receivers that were manufactured before
   July 1, 1993.

   (2) Effective January 1, 2014, all television broadcast receivers
   shipped in interstate commerce, manufactured, assembled, or imported
   from any foreign country into the United States shall comply with the
   provisions of this section, if technically feasible, except that
   television broadcast receivers that use a picture screen less than 13
   inches in size must comply with the provisions of this section only if
   doing so is achievable pursuant to § 79.103(b)(3).

   Note to paragraph (a)(2): This paragraph places no restrictions on the
   importing, shipping, or sale of television receivers that were
   manufactured before January 1, 2014.

   (b) Transmission format. Closed-caption information is transmitted on
   line 21 of field 1 of the vertical blanking interval of television
   signals, in accordance with § 73.682(a)(22) of this chapter.

   (c) Operating modes. The television receiver will employ
   customer-selectable modes of operation for TV and Caption. A third mode
   of operation, Text, may be included on an optional basis. The Caption
   and Text Modes may contain data in either of two operating channels,
   referred to in this document as C1 and C2. The television receiver must
   decode both C1 and C2 captioning, and must display the captioning for
   whichever channel the user selects. The TV Mode of operation allows the
   video to be viewed in its original form. The Caption and Text Modes
   define one or more areas (called “boxes”) on the screen within which
   caption or text characters are displayed.

   Note: For more information regarding Text mode, see “Television
   Captioning for the Deaf: Signal and Display Specifications”,
   Engineering Report No. E-7709-C, Public Broadcasting Service, dated May
   1980, and “TeleCaption II Decoder Module Performance Specification”,
   National Captioning Institute, Inc., dated November 1985. These
   documents are available, respectively, from the Public Broadcasting
   Service, 1320 Braddock Place, Alexandria, VA 22314 and from the
   National Captioning Institute, Inc., 5203 Leesburg Pike, Falls Church,
   VA 22041.

   (d) Screen format. The display area for captioning and text shall fall
   approximately within the safe caption area as defined in paragraph
   (n)(12) of this section. This display area will be further divided into
   15 character rows of equal height and 32 columns of equal width, to
   provide accurate placement of text on the screen. Vertically, the
   display area begins on line 43 and is 195 lines high, ending on line
   237 on an interlaced display. All captioning and text shall fall within
   these established columns and rows. The characters must be displayed
   clearly separated from the video over which they are placed. In
   addition, the user must have the capability to select a black
   background over which the captioned letters are displaced.

   (1) Caption mode. In the Caption Mode, text can appear on up to 4 rows
   simultaneously anywhere on the screen within the defined display area.
   In addition, a solid space equal to one column width may be placed
   before the first character and after the last character of each row to
   enhance legibility. The caption area will be transparent anywhere that
   either:

   (i) No standard space character or other character has been addressed
   and no accompanying solid space is needed; or,

   (ii) An accompanying solid space is used and a “transparent space”
   special character has been addressed which does not immediately precede
   or follow a displayed character.

   (2) [Reserved]

   (e) Presentation format. In analyzing the presentation of characters,
   it is convenient to think in terms of a non-visible cursor which marks
   the screen position at which the next event in a given mode and data
   channel will occur. The receiver remembers the cursor position for each
   mode even when data are received for a different address in an
   alternate mode or data channel.

   (1) Screen addressing. Two kinds of control codes are used to move the
   cursor to specific screen locations. In Caption Mode, these addressing
   codes will affect both row and column positioning. In Text Mode, the
   codes affect only column positioning. In both modes, the addressing
   codes are optional. Default positions are defined for each mode and
   style when no addressing code is provided.

   (i) The first type of addressing code is the Preamble Address Code
   (PAC). It assigns a row number and one of eight “indent” figures. Each
   successive indent moves the cursor four columns to the right (starting
   from the left margin). Thus, an indent of 0 places the cursor at Column
   1, an indent of 4 sets it at Column 5, etc. The PAC indent is
   non-destructive to displayable characters. It will not affect the
   display to the left of the new cursor position on the indicated row.
   Note that Preamble Address Codes also set initial attributes for the
   displayable characters which follow. See paragraph (h) of this section
   and the Preamble Address Code table.

   (ii) The second type of addressing code is the Tab Offset, which is one
   of three Miscellaneous Control Codes. Tab Offset will move the cursor
   one, two, or three columns to the right. The character cells skipped
   over will be unaffected; displayable characters in these cells, if any,
   will remain intact while empty cells will remain empty, in the same
   manner that a PAC indent is non-destructive.

   (2) [Reserved]

   (f) Caption Mode. There are three styles of presenting text in Caption
   Mode: roll-up, pop-on, and paint-on. Character display varies
   significantly with the style used, but certain rules of character
   erasure are common to all styles. A character can be erased by
   addressing another character to the same screen location or by
   backspacing over the character from a subsequent location on the same
   row. The entire displayed memory will be erased instantly by receipt of
   an Erase Displayed Memory command. Both displayed memory and
   non-displayed memory will be entirely erased simultaneously by either:
   The user switching receiver channels or data channels (C1/C2) or fields
   (F1/F2) in decoders so equipped; the loss of valid data (see paragraph
   (j) of this section); or selecting non-captioning receiver functions
   which use the display memory of the decoder. Receipt of an End of
   Caption command will cause a displayed caption to become non-displayed
   (and vice versa) without being erased from memory. Changing the
   receiver to a non-captioning mode which does not require use of the
   decoder's display memory will leave that memory intact, and the decoder
   will continue to process data as if the caption display were selected.

   (1) Roll-up. Roll-up style captioning is initiated by receipt of one of
   three Miscellaneous Control Codes that determine the maximum number of
   rows displayed simultaneously, either 2, 3 or 4 contiguous rows. These
   are the three Roll-Up Caption commands.

   (i) The bottom row of the display is known as the “base row”. The
   cursor always remains on the base row. Rows of text roll upwards into
   the contiguous rows immediately above the base row to create a “window”
   2 to 4 rows high.

   (ii) The Roll-Up command, in normal practice, will be followed (not
   necessarily immediately) by a Preamble Address Code indicating the base
   row and the horizontal indent position. If no Preamble Address Code is
   received, the base row will default to Row 15 or, if a roll-up caption
   is currently displayed, to the same base row last received, and the
   cursor will be placed at Column 1. If the Preamble Address Code
   received contains a different base row than that of a currently
   displayed caption, the entire window will move intact (and without
   erasing) to the new base row immediately.

   (iii) Each time a Carriage Return is received, the text in the top row
   of the window is erased from memory and from the display or scrolled
   off the top of the window. The remaining rows of text are each rolled
   up into the next highest row in the window, leaving the base row blank
   and ready to accept new text. This roll-up must appear smooth to the
   user, and must take no more than 0.433 second to complete. The cursor
   is automatically placed at Column 1 (pending receipt of a Preamble
   Address Code).

   (iv) Increasing or decreasing the number of roll-up rows instantly
   changes the size of the active display window, appropriately turning on
   or off the display of the top one or two rows. A row which is turned
   off should also be erased from memory.

   (v) Characters are always displayed immediately when received by the
   receiver. Once the cursor reaches the 32nd column position on any row,
   all subsequent characters received prior to a Carriage Return, Preamble
   Address Code, or Backspace will be displayed in that column replacing
   any previous character occupying that address.

   (vi) The cursor moves automatically one column to the right after each
   character or Mid-Row Code received. A Backspace will move the cursor
   one column to the left, erasing the character or Mid-Row Code occupying
   that location. (A Backspace received when the cursor is in Column 1
   will be ignored.)

   (vii) The Delete to End of Row command will erase from memory any
   characters or control codes starting at the current cursor location and
   in all columns to its right on the same row. If no displayable
   characters remain on the row after the Delete to End of Row is acted
   upon, the solid space (if any) for that row should also be erased to
   conform with the following provisions.

   (viii) If a solid space is used for legibility, it should appear when
   the first displayable character (not a transparent space) or Mid-Row
   Code is received on a row, not when the Preamble Address Code, if any,
   is given. A row on which there are no displayable characters or Mid-Row
   Codes will not display a solid space, even when rolled up between two
   rows which do display a solid space.

   (ix) If the reception of data for a row is interrupted by data for the
   alternate data channel or for Text Mode, the display of caption text
   will resume from the same cursor position if a Roll-Up Caption command
   is received and no Preamble Address Code is given which would move the
   cursor.

   (x) A roll-up caption remains displayed until one of the standard
   caption erasure techniques is applied. Receipt of a Resume Caption
   Loading command (for pop-on style) or a Resume Direct Captioning
   command (for paint-on style) will not affect a roll-up display. Receipt
   of a Roll-Up Caption command will cause any pop-on or paint-on caption
   to be erased from displayed memory and non-displayed memory.

   (2) Pop-on. Pop-on style captioning is initiated by receipt of a Resume
   Caption Loading command. Subsequent data are loaded into a
   non-displayed memory and held there until an End of Caption command is
   received, at which point the non-displayed memory becomes the displayed
   memory and vice versa. (This process is often referred to as “flipping
   memories” and does not automatically erase memory.) An End of Caption
   command forces the receiver into pop-on style if no Resume Caption
   Loading command has been received which would do so. The display will
   be capable of 4 full rows, not necessarily contiguous, simultaneous
   anywhere on the screen.

   (i) Preamble Address Codes can be used to move the cursor around the
   screen in random order to place captions on Rows 1 to 15. Carriage
   Returns have no effect on cursor location during caption loading.

   (ii) The cursor moves automatically one column to the right after each
   character or Mid-Row Code received. Receipt of a Backspace will move
   the cursor one column to the left, erasing the character or Mid-Row
   Code occupying that location. (A Backspace received when the cursor is
   in Column 1 will be ignored.) Once the cursor reaches the 32nd column
   position on any row, all subsequent characters received prior to a
   Backspace, an End of Caption, or a Preamble Address Code, will replace
   any previous character at that location.

   (iii) The Delete to End of Row command will erase from memory any
   characters or control codes starting at the current cursor location and
   in all columns to its right on the same row. If no displayable
   characters remain on a row after the Delete to End of Row is acted
   upon, the solid space (if any) for that element should also be erased.

   (iv) If data reception is interrupted during caption loading by data
   for the alternate caption channel or for Text Mode, caption loading
   will resume at the same cursor position if a Resume Caption Loading
   command is received and no Preamble Address Code is given that would
   move the cursor.

   (v) Characters remain in non-displayed memory until an End of Caption
   command flips memories. The caption will be erased without being
   displayed upon receipt of an Erase Non-Displayed Memory command, a
   Roll-Up Caption command, or if the user switches receiver channels,
   data channels or fields, or upon the loss of valid data (see paragraph
   (j) of this section).

   (vi) A pop-on caption, once displayed, remains displayed until one of
   the standard caption erasure techniques is applied or until a Roll-Up
   Caption command is received. Characters within a displayed pop-on
   caption will be replaced by receipt of the Resume Direct Captioning
   command and paint-on style techniques (see below).

   (3) Paint-on. Paint-on style captioning is initiated by receipt of a
   Resume Direct Captioning command. Subsequent data are addressed
   immediately to displayed memory without need for an End of Caption
   command.

   (i) Preamble Address Codes can be used to move the cursor around the
   screen in random order to display captions on Rows 1 to 15. Carriage
   Returns have no affect on cursor location during direct captioning. The
   cursor moves automatically one column to the right after each character
   or Mid-Row Code is received. Receipt of a Backspace will move the
   cursor one column to the left, erasing the character or Mid-Row Code
   occupying that location. (A Backspace received when the cursor is in
   Column 1 will be ignored.) Once the cursor reaches the 32nd column
   position on any row, all subsequent characters received prior to a
   Preamble Address Code or Backspace will be displayed in that column
   replacing any previous character occupying that location.

   (ii) The Delete to End of Row command will erase from memory any
   characters or control codes starting at the current cursor location and
   in all columns to its right on the same row. If no displayable
   characters remain on the row after the Delete to End of Row is acted
   upon, the solid space (if any) for that element should also be erased.

   (iii) If the reception of data is interrupted during the direct
   captioning by data for the alternate caption channel or for Text Mode,
   the display of caption text will resume at the same cursor position if
   a Resume Direct Captioning command is received and no Preamble Address
   Code is given which would move the cursor.

   (iv) Characters remain displayed until one of the standard caption
   erasure techniques is applied or until a Roll-Up Caption command is
   received. An End of Caption command leaves a paint-on caption fully
   intact in non-displayed memory. In other words, a paint-on style
   caption behaves precisely like a pop-on style caption which has been
   displayed.

   (g) Character format. Characters are to be displayed on the screen
   within a character “cell” which is the height and width of a single row
   and column. The following codes define the displayable character set.
   Television receivers manufactured prior to January 1, 1996 and having a
   character resolution of 5 × 7 dots, or less, may display the allowable
   alternate characters in the character table. A statement must be in a
   prominent location on the box or other package in which the receiver is
   to be marketed, and information must be in the owner's manual,
   indicating the receiver displays closed captioning in upper case only.

Character Set Table

Special Characters

   These require two bytes for each symbol. Each hex code as shown will be
   preceded by a 11h for data channel 1 or by a 19h for data channel 2.
   For example: 19h 37h will place a musical note in data channel 2.
   HEX Example  Alternate           Description
    30    ®    See  note^1 Registered mark symbol
    31    �°                Degree sign
    32  1⁄2                1⁄2
    33    ¿                Inverse query
    34   ^TM   See  note^1 Trademark symbol
    35    ¢                Cents sign
    36    £                Pounds Sterling sign
    37    ♪                Music note
    38    à         A      Lower-case a with grave accent
    39                     Transparent space
    3A    è         E      Lower-case e with grave accent
    3B    â         A      Lower-case a with circumflex
    3C    ê         E      Lower-case e with circumflex
    3D    î         I      Lower-case i with circumflex
    3E    ô         O      Lower-case o with circumflex
    3F    û         U      Lower-case u with circumflex

   ^1Note: The registered and trademark symbols are used to satisfy
   certain legal requirements. There are various legal ways in which these
   symbols may be drawn or displayed. For example, the trademark symbol
   may be drawn with the “T” next to the “M” or over the “M”. It is
   preferred that the trademark symbol be superscripted, i.e., XYZ^TM. It
   is left to each individual manufacturer to interpret these symbols in
   any way that meets the legal needs of the user.

Standard characters

   HEX Example Alternate          Description
    20                   Standard space
    21    !              Exclamation mark
    22    “              Quotation mark
    23    #              Pounds (number) sign
    24    $              Dollar sign
    25    %              Percentage sign
    26    &              Ampersand
    27    '              Apostrophe
    28    (              Open parentheses
    29    )              Close parentheses
    2A    á        A     Lower-case a with acute accent
    2B   +               Plus sign
    2C    ,              Comma
    2D    −              Minus (hyphen) sign
    2E    .              Period
    2F    /              Slash
    30    0              Zero
    31    1              One
    32    2              Two
    33    3              Three
    34    4              Four
    35    5              Five
    36    6              Six
    37    7              Seven
    38    8              Eight
    39    9              Nine
    3A    :              Colon
    3B    ;              Semi-colon
    3C    <              Less than sign
    3D    =              Equal sign
    3E    >              Greater than sign
    3F    ?              Question mark
    40    @              At sign
    41    A              Upper-case A
    42    B              Upper-case B
    43    C              Upper-case C
    44    D              Upper-case D
    45    E              Upper-case E
    46    F              Upper-case F
    47    G              Upper-case G
    48    H              Upper-case H
    49    I              Upper-case I
    4A    J              Upper-case J
    4B    K              Upper-case K
    4C    L              Upper-case L
    4D    M              Upper-case M
    4E    N              Upper-case N
    4F    O              Upper-case O
    50    P              Upper-case P
    51    Q              Upper-case Q
    52    R              Upper-case R
    53    S              Upper-case S
    54    T              Upper-case T
    55    U              Upper-case U
    56    V              Upper-case V
    57    W              Upper-case W
    58    X              Upper-case X
    59    Y              Upper-case Y
    5A    Z              Upper-case Z
    5B    [              Open bracket
    5C    é        E     Lower-case e with acute accent
    5D    ]              Close bracket
    5E    í        I     Lower-case i with acute accent
    5F    ó        O     Lower-case o with acute accent
    60    ú        U     Lower-case u with acute accent
    61    a        A     Lower-case a
    62    b        B     Lower-case b
    63    c        C     Lower-case c
    64    d        D     Lower-case d
    65    e        E     Lower-case e
    66    f        F     Lower-case f
    67    g        G     Lower-case g
    68    h        H     Lower-case h
    69    i        I     Lower-case i
    6A    j        J     Lower-case j
    6B    k        K     Lower-case k
    6C    l        L     Lower-case l
    6D    m        M     Lower-case m
    6E    n        N     Lower-case n
    6F    o        O     Lower-case o
    70    p        P     Lower-case p
    71    q        Q     Lower-case q
    72    r        R     Lower-case r
    73    s        S     Lower-case s
    74    t        T     Lower-case t
    75    u        U     Lower-case u
    76    v        V     Lower-case v
    77    w        W     Lower-case w
    78    x        X     Lower-case x
    79    y        Y     Lower-case y
    7A    z        Z     Lower-case z
    7B    ç        C     Lower-case c with cedilla
    7C   ÷               Division sign
    7D    Ñ              Upper-case N with tilde
    7E    ñ        Ñ     Lower-case n with tilde
    7F    ■              Solid block

   (h) Character Attributes—(1) Transmission of Attributes. A character
   may be transmitted with any or all of four attributes: Color, italics,
   underline, and flash. All of these attributes are set by control codes
   included in the received data. An attribute will remain in effect until
   changed by another control code or until the end of the row is reached.
   Each row begins with a control code which sets the color and underline
   attributes. (White non-underlined is the default display attribute if
   no Preamble Address Code is received before the first character on an
   empty row.) Attributes are not affected by transparent spaces within a
   row.

   (i) All Mid-Row Codes and the Flash On command are spacing attributes
   which appear in the display just as if a standard space (20h) had been
   received. Preamble Address Codes are non-spacing and will not alter any
   attributes when used to position the cursor in the midst of a row of
   characters.

   (ii) The color attribute has the highest priority and can only be
   changed by the Mid-Row Code of another color. Italics has the next
   highest priority. If characters with both color and italics are
   desired, the italics Mid-Row Code must follow the color assignment. Any
   color Mid-Row Code will turn off italics. If the least significant bit
   of a Preamble Address Code or of a color or italics Mid-Row Code is a 1
   (high), underlining is turned on. If that bit is a 0 (low), underlining
   is off.

   (iii) The flash attribute is transmitted as a Miscellaneous Control
   Code. The Flash On command will not alter the status of the color,
   italics, or underline attributes. However, any color or italics Mid-Row
   Code will turn off flash.

   (iv) Thus, for example, if a red, italicized, underlined, flashing
   character is desired, the attributes must be received in the following
   order: a red Mid-Row or Preamble Address Code, an italics Mid-Row Code
   with underline bit, and the Flash On command. The character will then
   be preceded by three spaces (two if red was assigned via a Preamble
   Address Code).

   (2) Display of attributes. The underline attribute will be displayed by
   drawing a line beneath the character in the same color as the
   character. The flash attribute will be displayed by causing the
   character to blink from the display at least once per second. The
   italic attribute must be capable of being displayed by either a special
   italic font, or by the modification of the standard font by slanting.
   The user may be given the option to select other methods of italic
   display as well. The support of the color attributes is optional. If
   the color attributes are supported, they will be displayed in the color
   they have been assigned. If color attributes are not supported, the
   display may be in color, but all color changes will be ignored.

   (i) Control codes. There are three different types of control codes
   used to identify the format, location, attributes, and display of
   characters: Preamble Address Codes, Mid-Row Codes, and Miscellaneous
   Control Codes.

   (1) Each control code consists of a pair of bytes which are always
   transmitted together in a single field of line 21 and which are
   normally transmitted twice in succession to help insure correct
   reception of the control instructions. The first of the control code
   bytes is a non-printing character in the range 10h to 1Fh. The second
   byte is always a printing character in the range 20h to 7Fh. Any such
   control code pair received which has not been assigned a function is
   ignored. If the non-printing character in the pair is in the range 00h
   to 0Fh, that character alone will be ignored and the second character
   will be treated normally.

   (2) If the second byte of a control code pair does not contain odd
   parity (see paragraph (j) of this section), then the pair is ignored.
   The redundant transmission of the pair will be the instruction upon
   which the receiver acts.

   (3) If the first byte of the first transmission of a control code pair
   fails the parity check, then that byte is inserted into the currently
   active memory as a solid block character (7Fh) followed by whatever the
   second byte is. Again, the redundant transmission of the pair will be
   the controlling instruction.

   (4) If the first transmission of a control code pair passes parity, it
   is acted upon within one video frame. If the next frame contains a
   perfect repeat of the same pair, the redundant code is ignored. If,
   however, the next frame contains a different but also valid control
   code pair, this pair, too, will be acted upon (and the receiver will
   expect a repeat of this second pair in the next frame). If the first
   byte of the expected redundant control code pair fails the parity check
   and the second byte is identical to the second byte in the immediately
   preceding pair, then the expected redundant code is ignored. If there
   are printing characters in place of the redundant code, they will be
   processed normally.

   (5) There is provision for decoding a second data channel. The second
   data channel is encoded with the same control codes and procedures
   already described. The first byte of every control code pair indicates
   the data channel (C1/C2) to which the command applies. Control codes
   which do not match the data channel selected by the user, and all
   subsequent data related to that control code, are ignored by the
   receiver.

   Mid-Row Codes
   Data channel 1 Data channel 2 Attribute description
          11   20        19   20 White.
          11   21        19   21 White Underline.
          11   22        19   22 Green.
          11   23        19   23 Green Underline.
          11   24        19   24 Blue.
          11   25        19   25 Blue Underline.
          11   26        19   26 Cyan.
          11   27        19   27 Cyan Underline.
          11   28        19   28 Red.
          11   29        19   29 Red Underline.
          11   2A        19   2A Yellow.
          11   2B        19   2B Yellow Underline.
          11   2C        19   2C Magenta.
          11   2D        19   2D Magenta Underline.
          11   2E        19   2E Italics.
          11   2F        19   2F Italics Underline.

   Miscellaneous Control Codes
   Data channel 1 Data channel 2 Mne-
   monic Command description
   14   20 1C   20 RCL Resume caption loading.
   14   21 1C   21 BS Backspace.
   14   22 1C   22 AOF Reserved (formerly Alarm Off).
   14   23 1C   23 AON Reserved (formerly Alarm On).
   14   24 1C   24 DER Delete to End of Row.
   14   25 1C   25 RU2 Roll-Up Captions-2 Rows.
   14   26 1C   26 RU3 Roll-Up Captions-3 Rows.
   14   27 1C   27 RU4 Roll-Up Captions-4 Rows.
   14   28 1C   28 FON Flash On.
   14   29 1C   29 RDC Resume Direct Captioning.
   14   2A 1C   2A TR Text Restart.
   14   2B 1C   2B RTD Resume Text Display.
   14   2C 1C   2C EDM Erase Displayed Memory.
   14   2D 1C   2D CR Carriage Return.
   14   2E 1C   2E ENM Erase Non-Displayed Memory.
   14   2F 1C   2F EOC End of Caption (Flip Memories).
   17   21 1F   21 TO1 Tab Offset 1 Column.
   17   22 1F   22 TO2 Tab Offset 2 Columns.
   17   23 1F   23 TO3 Tab Offset 3 Columns.

   Preamble Address Codes
       Row 1 Row 2 Row 3 Row 4 Row 5 Row 6 Row 7 Row 8 Row 9 Row 10 Row 11
   Row 12 Row 13 Row 14 Row 15
   First byte of code pair:
   Data Channel 1 11 11 12 12 15 15 16 16 17 17 10 13 13 14 14
   Data Channel 2 19 19 1A 1A 1D 1D 1E 1E 1F 1F 18 1B 1B 1C 1C
   Second byte of code pair:
   White 40 60 40 60 40 60 40 60 40 60 40 40 60 40 60
   White Underline 41 61 41 61 41 61 41 61 41 61 41 41 61 41 61
   Green 42 62 42 62 42 62 42 62 42 62 42 42 62 42 62
   Green Underline 43 63 43 63 43 63 43 63 43 63 43 43 63 43 63
   Blue 44 64 44 64 44 64 44 64 44 64 44 44 64 44 64
   Blue Underline 45 65 45 65 45 65 45 65 45 65 45 45 65 45 65
   Cyan 46 66 46 66 46 66 46 66 46 66 46 46 66 46 66
   Cyan Underline 47 67 47 67 47 67 47 67 47 67 47 47 67 47 67
   Red 48 68 48 68 48 68 48 68 48 68 48 48 68 48 68
   Red Underline 49 69 49 69 49 69 49 69 49 69 49 49 69 49 69
   Yellow 4A 6A 4A 6A 4A 6A 4A 6A 4A 6A 4A 4A 6A 4A 6A
   Yellow Underline 4B 6B 4B 6B 4B 6B 4B 6B 4B 6B 4B 4B 68 4B 6B
   Magenta 4C 6C 4C 6C 4C 6C 4C 6C 4C 6C 4C 4C 6C 4C 6C
   Magenta Underline 4D 6D 4D 6D 4D 6D 4D 6D 4D 6D 4D 4D 6D 4D 6D
   White Italics 4E 6E 4E 6E 4E 6E 4E 6E 4E 6E 4E 4E 6E 4E 6E
   White Italics Underline 4F 6F 4F 6F 4F 6F 4F 6F 4F 6F 4F 4F 6F 4F 6F
   Indent 0 50 70 50 70 50 70 50 70 50 70 50 50 70 50 70
   Indent 0 Underline 51 71 51 71 51 71 51 71 51 71 51 51 71 51 71
   Indent 4 52 72 52 72 52 72 52 72 52 72 52 52 72 52 72
   Indent 4 Underline 53 73 53 73 53 73 53 73 53 73 53 53 73 53 73
   Indent 8 54 74 54 74 54 74 54 74 54 74 54 54 74 54 74
   Indent 8 Underline 55 75 55 75 55 75 55 75 55 75 55 55 75 55 75
   Indent 12 56 76 56 76 56 76 56 76 56 76 56 56 76 56 76
   Indent 12 Underline 57 77 57 77 57 77 57 77 57 77 57 57 77 57 77
   Indent 16 58 78 58 78 58 78 58 78 58 78 58 58 78 58 78
   Indent 16 Underline 59 79 59 79 59 79 59 79 59 79 59 59 79 59 79
   Indent 20 5A 7A 5A 7A 5A 7A 5A 7A 5A 7A 5A 5A 7A 5A 7A
   Indent 20 Underline 5B 7B 5B 7B 5B 7B 5B 7B 5B 7B 5B 5B 7B 5B 7B
   Indent 24 5C 7C 5C 7C 5C 7C 5C 7C 5C 7C 5C 5C 7C 5C 7C
   Indent 24 Underline 5D 7D 5D 7D 5D 7D 5D 7D 5D 7D 5D 5D 7D 5D 7D
   Indent 28 5E 7E 5E 7E 5E 7E 5E 7E 5E 7E 5E 5E 7E 5E 7E
   Indent 28 Underline 5F 7F 5F 7F 5F 7F 5F 7F 5F 7F 5F 5F 7F 5F 7F

   Note: All indent codes (second byte equals 50h-5fh, 70th-7fh) assign
   white as the color attribute.

   (j) Data rejection. The receiver should provide an effective procedure
   to verify data. A receiver will reject data if the data is invalid, or
   if the data is directed to the data channel or field not selected by
   the user. Invalid data is any data that fails to pass a check for odd
   parity, or which, having passed the parity check, is assigned no
   function.

   (1) If a print character fails to pass a check for parity, a solid
   block (7Fh) should be displayed in place of the failed character. In
   addition, valid data can be corrupted in many ways and may not be
   suitable for display. For example, repeated fields, skipped fields and
   altered field sequences are all possible from consumer video equipment
   and might present meaningless captions.

   (2) The receiver will ignore data rejected due to being directed to a
   deselected field or channel. However, this will not cause the display
   to be disabled.

   (k) Automatic display enable/disable. The receiver shall provide an
   automatic enable/disable capability to prevent the display of invalid
   or incomplete data, when the user selects the Caption Mode. The display
   should automatically become enable after the receiver verifies the data
   as described in paragraph (j) of this section. The display will be
   automatically disabled when there is a sustained detection of invalid
   data. The display will be re-enabled when the data verification process
   has been satisfied once again.

   (l) Compatibility with Cable Security Systems. Certain cable television
   security techniques, such as signal encryption and copy protection, can
   alter the television signal so that some methods of finding line 21
   will not work. In particular, counting of lines or timing from the
   start of the vertical blanking interval may cause problems. Caption
   decoding circuitry must function properly when receiving signals from
   cable security systems that were designed and marketed prior to April
   5, 1991. Further information concerning such systems is available from
   the National Cable Television Association, Inc., Washington, DC, and
   from the Electronic Industries Association, Washington, DC.

   (m) [Reserved]

   (n) Glossary of terms. The following terms are used to describe caption
   decoder specifications:

   (1) Base row: The bottom row of a roll-up display. The cursor always
   remains on the base row. Rows of text roll upwards into the contiguous
   rows immediately above the base row.

   (2) Box: The area surrounding the active character display. In Text
   Mode, the box is the entire screen area defined for display, whether or
   not displayable characters appear. In Caption Mode, the box is
   dynamically redefined by each caption and each element of displayable
   characters within a caption. The box (or boxes, in the case of a
   multiple-element caption) includes all the cells of the displayed
   characters, the non-transparent spaces between them, and one cell at
   the beginning and end of each row within a caption element in those
   decoders that use a solid space to improve legibility.

   (3) Caption window: The invisible rectangle which defines the top and
   bottom limits of a roll-up caption. The window can be 2 to 4 rows high.
   The lowest row of the window is called the base row.

   (4) Cell: The discrete screen area in which each displayable character
   or space may appear. A cell is one row high and one column wide.

   (5) Column: One of 32 vertical divisions of the screen, each of equal
   width, extending approximately across the full width of the safe
   caption area as defined in paragraph (n)(12) of this section. Two
   additional columns, one at the left of the screen and one at the right,
   may be defined for the appearance of a box in those decoders which use
   a solid space to improve legibility, but no displayable characters may
   appear in those additional columns. For reference, columns may be
   numbered 0 to 33, with columns 1 to 32 reserved for displayable
   characters.

   (6) Displayable character: Any letter, number or symbol which is
   defined for on-screen display, plus the 20h space.

   (7) Display disable: To turn off the display of captions or text (and
   accompanying background) at the receiver, rather than through codes
   transmitted on line 21 which unconditionally erase the display. The
   receiver may disable the display because the user selects an alternate
   mode, e.g., TV Mode, or because no valid line 21 data is present.

   (8) Display enable: To allow the display of captions or text when they
   are transmitted on line 21 and received as valid data. For display to
   be enabled, the user must have selected Caption Mode or Text Mode, and
   valid data for the selected mode must be present on line 21.

   (9) Element: In a pop-on or paint-on style caption, each contiguous
   area of cells containing displayable characters and non-transparent
   spaces between those characters. A single caption may have multiple
   elements. An element is not necessarily a perfect rectangle, but may
   include rows of differing widths.

   (10) Erase Display: In Caption Mode, to clear the screen of all
   characters (and accompanying background) in response to codes
   transmitted on line 21. (The caption service provider can accomplish
   the erasure either by sending an Erase Displayed Memory command or by
   sending an Erase Non-Displayed Memory command followed by an End of
   Caption command, effectively making a blank caption “appear”.) Display
   can also be erased by the receiver when the caption memory erasure
   conditions are met, such as the user changing TV channels.

   (11) Row: One of 15 horizontal divisions of the screen, extending
   across the full height of the safe caption area as defined in paragraph
   (n)(12) of this section.

   (12) Safe caption area: The area of the television picture within which
   captioning and text shall be displayed to ensure visibility of the
   information on the majority of home television receivers. The safe
   caption area is specified as shown in the following figure:
   eCFR graphic ec03jn91.009.gif

   View or download PDF

   The dimensions of the above figure shall be as follows:
   Label Dimensions Percent of television picture height
   A Television picture height 100.0
   B Television picture width 133.33
   C Height of safe caption area 80.0
   D Width of safe caption area 106.67
   E Vertical position of safe caption area 10.0
   F Horizontal position of safe caption area 13.33

   (13) Special characters: Displayable characters (except for
   “transparent space”) which require a two-byte sequence of one
   non-printing and one printing character. The non-printing byte varies
   depending on the data channel. Regular characters require unique
   one-byte codes which are the same in either data channel.

   (14) Text: When written with an upper-case “T”, refers to the Text
   Mode. When written with a lower-case “t”, refers to any combination of
   displayable characters.

   (15) Transparent space: Transmitted as a special character, it is a
   one-column-wide space behind which program video is always visible
   (except when a transparent space immediately precedes or follows a
   displayable character and solid box is needed to make that character
   legible).

   [ 56 FR 27201 , June 13, 1991, as amended at  57 FR 19094 , May 4, 1992;  58 FR 44893 , Aug. 25, 1993. Redesignated and amended at  77 FR 19515 ,
   19518, Mar. 30, 2012;  78 FR 39627 , July 2, 2013;  78 FR 77251 , Dec. 20,
   2013]

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