More that you ever wanted to know about international
standards ISO 11784 and ISO 11785 regarding animal identification
transponders:
If you read
the web for information about the two international standards ISO 11784
and ISO 11785 you may learn things
like: 1. ISO 11784 describes
the chip/transponder and ISO
11785 describes the scanner/reader. 2.
They specify a
transponder with an ID code that is 15 digits long. 3. They
specify, among other things, a transponder type called "FDX-A" and a
transponder type called "FDX-B". 4.
They describe more than
one type of transponder commonly used
for pets, and all are described "as compliant" to the standard. 5. Chips marketed in the US under
names such as AVID EUROChip or
HomeAgain operate as described in an ISO 11785 Annex. 6. ISO 11784 and ISO 11785 are open
standards. But are any of these
statements really true? Here are my comments.
Is it true as some sources state that ISO 11784 describes the
chip/transponder and ISO 11785 describes the scanner/reader? No. ISO
11785 describes protocols
to be used by transponders and
readers (which it calls
"transceivers") and gives some details about their construction. ISO
11784 only tells how the 64-bit identification
code stored on
transponders in conformance to ISO 11785 is to be built up. There are
38 bits for the main identification code, to be a "Unique
number within a country," 10 bits for a country code, and a one-bit
flag to indicate if an additional block of data, such
as "physiological data," is provided. (Not currently common in
pet
applications.) Then there are 14 bits left as "reserved,"
at least in the current August 1996 edition, and there's one bit to
indicate whether the transponder is for an animal application or
non-animal. (No guidance is given as to whether human beings are
animals...) That's the order of transmission of the bit fields;
the numeric values are transmitted "Least Significant Bit first"
according to ISO 11785. For the country code field, codes 900
through 998 "may be used" to refer to individual manufacturers. These
commonly are seen in transponders in pets. Country code
999 indicates a "test transponder" whose number may not be
unique. In all cases the standard still calls it a country code.
But is it true that the ISO standards specify a transponder with an ID
code that is 15 digits long? Maybe. Well, the 38 bit field
expressed as
a decimal number gives a value from 0 to 274877906943, so that's 12
digits right there. The 10 bit country code field has values from
0 through 1023 giving 4 digits. The country code according to ISO
11784 is an "ISO 3166 numeric-3 country code" which you might
assume should only take 3 digits, but right next to that description
is the legend that the number of combinations is 1024. I
don't see any definite statement in
ISO 11784 or ISO 11785 that a country code can not be in the
range 1000 to 1023; so although it may be unlikely that these codes
will be used for any transponders, a reader should probably
accommodate them,
meaning 16 decimal digits total. But even if you assume that only
country codes up to 999 need to be supported, there's nothing in the
standard to support combining the two decimal numbers to make one long
number. If there was, there would have to be an instruction
telling whether to put the Country
Code first or last. That instruction isn't there. You might say that
putting the Country Code first, as is commonly
done, is the obvious order, but that's not the order the
transponder transmits them in. The Max Microchip software prints
the full 4 digits for the Country Code, and puts a separating space
character
between that and the 12 digit part.
And is it true that the ISO standards specify a transponder type
called "FDX-A" and a transponder type called "FDX-B"? I've
looked carefully, and the only place I see anything like this is
one mention of "FDX B technology" in the Introduction section
of ISO 11785. It is used without any dash or
hyphen, and it appears in the context of talking about patents held by
one specific company. I don't see FDX-A or FDX-B used to describe
any of the transponder types or protocols, old or new, that are
detailed in the ISO 11785 main body or any of its annexes. And
these terms don't appear in the definitions section or the table of
Abbreviations. So the Max Microchip unit doesn't use these
descriptions. Actually it would have made a lot of sense for the
standard to give the protocols names like FDX-A, FDX-B, FDX-C,
and FDX-D, but it doesn't.
Some sources claim that the ISO standards describe more than one type
of
transponder commonly used for pets, and all are described "as
compliant" to the standard. Is this true? When I look at
ISO 11785, I see the protocols of five transponder types
described
in the standard. Section 6.1 describes a "Full duplex system" protocol
which is now widely used for pets around the world. Section 6.2
describes a "Half duplex system" which is usually implemented in
relatively large implantable chips or ear tags for livestock. These are
not likely to be found in pets unless you include, for
example, a pet cow or pet elephant. Then there are three
more types listed in Annex A. Section A.2.1 describes a "Destron
(FECAVA version) technology" type, with 35 information bits; section
A.2.2 describes a "Datamars technology" type, with 48 information
bits; and section A.2.3 describes a "Trovan technology" type,
with 39 information bits. (These are the names given in the
paragraph headings, and it sure would be nice if shorter names
were given.) But does this mean we can have 5 types of compliant
transponder? It might seem so, since there is a statement in the
Foreword on page ii of the standard that says "Annexes A and B form an
integral part of this International Standard." But section
2 on "Conformance" doesn't support 5 compliant types. It says
"Transponders are in conformance with this International
Standard provided they meet the requirements given in clause 6 of
this International Standard." So at least if "compliant" means
the same thing as "in conformance," there are only two kinds of
transceivers that are compliant. So why are the three types
described in the Annex included at all? Section 2 makes that
clear also. It's because Transceivers
(readers/scanners) may need to read them, at least for a period of
time. ISO 11785 describes
5 types of transponders,
all of which may be readable on a fully capable reader, but only
two of which are themselves in conformance to the standard. The
other
three, although they were never in conformance, are and
will always be, described in
ISO 11785. The Max Microchip
reader makes use of the appropriate paragraph headings from ISO
11785 as authoritative names for the protocols that it decodes
following descriptions in the standard.
I've also seen it claimed that transponders marketed in the US
under names such as AVID EUROChip or HomeAgain operate as described in
Annex A. From the limited specimens I've seen
of these types, I found this not to be true. They
show up as described for chips of the "Destron (FECAVA version)
technology" type, except completely backwards. The "Destron
(FECAVA version) technology" type calls for use of
Frequency-Shift-Keying, meaning the information is encoded by two
specific frequencies in the detected signal. I
found my specimens, one each EUROChip and HomeAgain, put out a High
(frequency) when the standard calls for a Low, and a Low when it calls
for
a High. So the Max Microchip reader will report these as
"Inv. ISO 11785 A.2.1" type transponders, where the "Inv." stands for
inverted.
And for a final question, are ISO 11784 and ISO 11785
open
standards? Not in the sense of the Open Standards the
Internet was built on. I paid 90 bucks at webstore.ansi.org
for my copies of ISO 11784 and ISO 11785; they may be
slightly cheaper directly from the
ISO's site depending on the Swiss Franc exchange rate at the
time. With a true open standard, like my own rec.pets-2005a, you
can reasonably assume that at least some of the people you read talking
about it on the 'net, have actually read the document.
There's one more sloppy thing about the ISO standards
to discuss. In the three protocol descriptions in Annex A, they
don't say how to convert the binary coded information bits into a
printable number. A direct conversion to a decimal number
representation might be inferred as reasonable, but in the case
of the 39-bit "Trovan technology" type, the code numbers I received
with my specimens were Base-16 hexadecimal, so I adopted this
convention for that chip type. In the case of the
35-bit "Destron (FECAVA version) technology" type, the code numbers I
received with my specimens looked like Base-16 hexadecimal, but
on closer observation, each of them when interpreted as
standard Base-16 gave a bigger number that the largest possible 35-bit
binary number. To make the numbers match, I had to use a
rather odd conversion method, where each 7-bit piece of the 35
bit binary number is converted to a two-digit Base-16 hexadecimal
representation, for a total of 10 characters in the result. The
Max Microchip reader uses this convention for both Inverted and
coded-per-standard variations of 35-bit types, although
as I
said, I haven't found a specimen that was coded-per-standard; indeed
they
may not
exist at all.
For the current version of the Max Microchip design, the "Half
duplex
system" type chips are not supported, and they may never
be. The "Datamars technology" type is not currently supported; I
couldn't get specimen chips. These
two types are uncommon in the U.S. pet population. Support
for "Trovan technology" type chips should be considered as
experimental quality at best; the Max Microchip machine's simple
hardware is not well suited
for the signal they transmit. (Not many U.S. pets have these either.)
When detected, they may
produce output like
this:
ISO 11785 A.2.3 "Trovan technology":
0001EF44C1
(127260)
ISO 11785 A.2.3 "Trovan technology":
0001BE32F8
(127137)
Inv. ISO 11785 A.2.1 "Destron (FECAVA version) technology": 136215372A
(126037)
Inv. ISO 11785 A.2.1 "Destron (FECAVA version) technology": 46781B102A
(126265)
ISO 11785 A.2.1 "Destron (FECAVA version) technology":
0001234567 (126113)
Note that the terms such as "Trovan", "Destron", and "FECAVA" which
appear in the output from the Max Microchip reader are not an
indication
that specifications from the Trovan and Destron companies, or from the
"Federation of European Companion Animal Veterinary Associations", have
been used in the decoding. These terms are used only as part of
the ISO 11785 paragraph headings which are applicable to the waveform
received. These names are unwieldy, but as exact paragraph
headings, they are the most correct and precise names for the protocols
that I could pull out of ISO 11785, which is the most
authoritative reference available. If I didn't want
to be precise, I might just have it print the code number and be done
with it.
Finally, for the case of actual ISO conformant
transponders, you may
see something like this:
ISO 11785 6.1 "Full duplex system": 0985
120027629061
(1,8000,126071)
ISO 11785 6.1 "Full duplex system": 0985
120028223912
(1,8000,126071)
For these, there is additional information in the parentheses on the
right. Here the "1" is the animal/non-animal bit, where "1" =
"animal". And between that and the frequency estimate is a
Base-16 hexadecimal representation of all 16 leftover bits (the
14 Reserved bits and 2 Flags) from the chip's 64-bit code
data, after the 48 bits used for the Country Code and main ID number
are removed. The animal/non-animal bit appears again as the most
significant bit of this code.
In all cases, the limited amount of space available in an 80-character
output line precluded including a clarification of which of the
detected transponder types are in
conformance to ISO 11785,
and which are only described
in ISO 11785.
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