19/09/18
Page 56 of 67
ASR650 Operational Manual
4.10 Synchronization
If two or more readers operate in close vicinity to each other, they have to be synchronized.
The example on the right shows that
the readers are not synchronized. If
reader 1 tries to read an HDX tag when
the field is switched off, it might fail in
this scenario. The reason is that
readers 2 and 3 have their fields
activated at this time; that means, they
transmit on the same frequency like
the HDX trans-ponder
– but with much
more power. If the unsynchronized
readers are too close to each other (up
to 50 meters, depending on antenna
size and orientation), they will not be
able to pick up an HDX transponder
signal
– at least not at the maximum
possible distance.
The solution for this problem is
‘Synchronization’. There are particular mechanisms which ensure
that the timing of several readers is strictly synchronized.
In this example the ASRs are
synchronized. The field on / off cycles
are synchronous. There is always
one
Sync. Master, all other ASRs are Sync.
Slaves.
Since all readers have the HDX-
listening period at the same time, there
is no more interference between the
fields and the transponder signal can
be picked up.