The ITU-T H.3xx Recommendation Series provides a
mechanism for equipment manufacturers to add
non-standard facilities (capabilities, commands, etc.)
that are unique the their specific equipment. This
mechanism uses the ITU-T Recommendation T.35
"Procedures for allocation of CCITT defined codes
for non-standard facilities". This Recommendation
specifies the format of the non-standard facility code
as having three parts: Country Code, Terminal Provider
Code, and Terminal Provider Oriented Code.
The Country Code identifies the country where the
manufacturer is located. This code is defined in T.35
Annex A. Currently, this is a one-byte code, however, in
order to accommodate more country codes, there is a
proposed revision that will extend this to a two-byte
code. This proposed revision uses the country code value
of hexadecimal FF as an extension indicator. When the
extension code is present, a second byte will contain
the extended country code value.
The Terminal Provider Code (or Manufacturer Code)
identifies the manufacturer within that country. An
Assignment Authority appointed by the national body
assigns this code nationally. Some of these Assignment
Authorities are listed below.
The Terminal Provider Oriented Code is a
manufacturer-defined code, which specifies the
The document APC-1576.pdf
describes the use of the non-standard facilities within
the various H-Series Recommendations. In most cases,
there is a one-byte country code which is defined in
T.35 Annex A, a one byte country code (t35) extension
which is defined nationally, a two byte manufacturer
code which is defined nationally, and then the
non-standard information which is defined by the
manufacturer and can be up to 255 bytes.
T.35 has recently been updated to use an extension
marker and a second byte in order to accommodate
additional country codes. A draft version of this
proposed T.35 can be found in t35rev.pdf.
The impact of this change on H.3xx series devices has
not been completely resolved. The document, d322.pdf
defines how the extended codes are used in H.320
systems. The effect of the extended codes on H.323/H.324
systems has not yet been determined, but will probably
be handled in a similar manner.
The authority to assign manufacturer codes within North America
resides with the Alliance for Telecommunications
Industry Solutions (ATIS). Currently, Delta Information
Systems, Inc. is assigning codes on behalf of ATIS.
The manufacturer code is always used in conjunction with
a country code. The country codes are defined in ITU-T
Recommendation T.35. The country code for the United
States is B5 (Hex). The country code for Canada is 20H.
The second byte of the country code is subject to
assignment by the national body. At present it is
assigned the value 00 (Hex). The manufacturer code is a
To request a manufacturer code assignment for a North
American company, please provide the following
In addition, the manufacturer code is a two-byte code, you may
request a specific two-byte code, or you may request to
be assigned a code from a sequential list.
This request including the required information can be
Delta Information Systems, Inc.
300 Welsh Road, Bldg. 3
Horsham, PA 19044-2273
The current list of assigned manufacturer codes for North America
can be found in the document manucode.pdf.