These symbols are defined by the Association of Radio Industries and Businesses (ARIB) in standards shown in its List of ARIB Standards in the Field of Broadcasting.
The symbols are defined in
ARIB STD-B3 "ARIB Standard for Operation of The FM Multiplex Broadcasting System" and in
ARIB STD-B24 "Data Coding and Transmission Specification for Digital Broadcasting" Volume 1 ("Fascicle 1"), Chapter 7 "Character coding", Table 7-10 "Additional Symbols" and Table 7-4 "Kanji Set" and Chapter 7.2 "Universal multi-octet coded Character Set".
Compared with ARIB STD-B3, ARIB STD-B24 adds 38 symbols in JIS row 90, cells 45..63 and 66..84, for a total of 394 symbols (as of version 5.1 of ARIB STD-24).
The proposal shows "ARIB code" values in the tables of symbols that are proposed to be encoded. This 4-digit "ARIB code" is derived from the ARIB characters' JIS code row/cell values by padding the cell number to two digits and concatenating the row and cell values to a 4-digit number. For example, where the proposal shows an "ARIB code" of 9001, it refers to the ARIB standards' character assigned to JIS row 90 and cell 1.
2009-01-16: L2/09-014 ISO/IEC 10646 - FPDAM 6 (additional files are HERE including cover letter)
2008-08-19: L2/08-253 UTC 116 / L2 213 Joint Meeting Minutes
[116-C25] Consensus: Encode U+26BD SOCCER BALL, and move amendment 6 characters 26BD and 26BE down by one codepoint to 26BE, 26BF.
2008-08-12: L2/08-307 Feedback on the Japanese TV Symbols Proposal (L2/08-077R3)
2008-08-06: L2/08-292 Improvement suggestions for n3469
2008-08-05: L2/08-289 Proposal to rename and reassign some Japanese TV Symbols from L2/08-077R3
2008-06-24: L2/08-246 Proposed Draft Amendment (PDAM) 6.2, Universal Multiple-Octet Coded Character Set (UCS) - Amendment 6: Javanese, Lisu, Meetei Mayek, Samaritan, and other characters [names list is HERE] (esp. pages 46..60, 63..69, 118..123)
2008-05-08: L2/08-215 Comments on L2/08-077R2 "Japanese TV Symbols"
2008-05-02: L2/08-077R3 Japanese TV symbols (revision 3; WG2 N3341, WG2 N3469)
2008-05-02: L2/08-188 Collected comments on Japanese TV Symbols WG2 N3397 (WG2 N3468)
2008-04-18: L2/08-158 Comments on L2/08-077R2 "Japanese TV Symbols"
2008-03-22: L2/08-128 Names and allocation of some Japanese TV symbols from N3397
2008-03-11: L2/08-077R2 Japanese TV Symbols (revision 2; WG2 N3397)
2008-02-27: L2/08-077R Japanese TV Symbols
2008-01-18: L2/08-077 Japanese TV Symbols
2007-10-17: L2/07-391 Japanese TV Symbols (replaces L2/07-259) = WG2 N 3341
2007-08-06: L2/07-259 Japanese TV Symbols