UK Allocation of Manufacturer Codes for H.221/H.245/T.120
This document is maintained by the UK Manufacturer Code Registrar, Bill
The document describes the procedures for allocation of manufacturer codes in
the United Kingdom together with some information about other countries.
The register of codes is detailed here.
The ITU-T has a useful page of information on the subject of manufacturer codes here.
Procedures for Allocation of UK Manufacturer Codes for H.221/H.245/T.120
Recommendation H.221 ("Frame Structure for a 64 to 1920 kbit/s Channel in
Audiovisual Services") permits manufacturers to add non-standard capabilities
to their products. This is achieved by providing each manufacturer with a
unique code so that compatible terminals may be identified. This code is
contained within the Bitstream Allocation Signal (BAS) and is defined in
section A.9 of H.221. The code sequence contains a two-octet country code, a
two-octet manufacturer code and up to 251 octets specified by the
The first octet of the country code is defined in Recommendation T.35 but the
second octet is allocated on a national basis as are the two octets of the
manufacturer code. Note that the current version of T.35 includes an
extension mechanism so that extra country codes may be added; it is recommended
that new implementations are designed to be compatible with this mechanism.
The same codes are also used in H.245 and the T.120 series which are used in
more modern types of multimedia system. This will create extra demand for
codes as H.323 and H.324 terminals appear.
A manufacturer wishing to obtain a code should contact either the DTI/RA person
responsible for ITU-T affairs or the coordinator for Study Group 16. The
coordinator will allocate a code taking into account any preferences expressed
by the applicant and will publish the new code in a master list on this Web
site. When informing the applicant of the code, the coordinator will also
include the current list of allocated codes.
When applying for a code a manufacturer should give the following
Telephone number (switchboard)
Company registration number (for future tracing)
Name of contact person
Telephone number (direct)
Email address of contact
Principles of Allocation
The first octet of the country code is defined in Recommendation T.35; the
value for the UK is 10110100 (B4h). There are three octets available for UK
1. The second octet of the country code.
2. The two-octet manufacturer code.
The second octet of the country code has historically been set to 00h and this
should not be changed unless there is a good reason that is acceptable to all
The first octet of the manufacturer code may be allocated to any number that
is spare although the value 11111111 (FFh) should be reserved as a possible
extension mechanism. At present, the second manufacturer octet is always
00000000 (00h); this octet should be kept at that value until the first octet
is used up. This will ensure compatibility with older equipment which may have
assumed that the second octet is always 00h.
Codes used in Other Countries
This information is very sketchy at the moment but it is intended to contain
information about allocation authorities and the codes they have allocated.
Please send details of any additions and amendments to the UK co-ordinator.
The ITU-t is now maintaining a database of allocation authorities; it may be downloaded here.
UK Registrar's Details
Tel: +44 1491 681236
Fax: +44 870 432 1905
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