Specifications

5.3. TRANSPONDER DATA FORMAT AND PROTOCOL
bands are detrimental to the penguins. The newwer e lectronic system already
in place is ISO 11784/85 compliant and the replacement system needs to be
backward-compatible with existing tags. Since these tags are sealed passive
units, they are expected to outlast the lifetimes of the birds.
The devices on offer in TI’s Series 2000 for animal tagging includes 24mm
and 32mm glass capsules. These tags are available in Read-Write or Read-
Only models. Figure 5.2 shows the 32mm Read-Only passive glass tags in
use on the island.
Figure 5.2: 32mm glass encapsulated transponder
5.3 Transponder Data Format and Protocol
As mentioned previously, the read-only transponders in use conform to ISO11784/85
standards. A read from one of these transponders is a two step process:
1. Charge tag; and
2. Read response
The tags are charged for approximately 50ms and then a read is initiated
which requires a maximum time of 20ms to complete. The tag do not
begin transmitting until it has detected that the charge signal has ended.
The charge time can thus be adjusted de pending upon factors such as the
application, transponder and antenna type and regulatory issues. A longer
charge time provides more energy for the tag and thus results in a more
powerful signal. Because the tags wait for the charge pulse to complete
before transmitting, they are considered half-duplex devices.
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