User Manual

Chapter 6 System Overview
- 68 - Hi-G-Tek Ltd. Micro electro nic s & A sset Tra cking Techno logy
points with DataT erminals along the way. In this scenario, you can know
the DataSeal's track by reading its Events, without having to have these
DataReaders connected to any central system.
6.2.2 DataReader Modes of Operation
There are several aspects that determine the DataReader's mode of
operation. T hese aspects are determined by the Mode parameter, which is a
bit orient ed parameter.
5. Carrier Sense Collision Prevention
Just like you can't understand what two people are saying when the speak
simultaneously, that way a DataSeal can't understand two DataReaders that
transmit simultaneously. When two (or more) close DataReaders aren't
controlled by the same controlling computer (or by controlling computers
that are synchronized among them), there's a chance that they will try to
transmit simultaneously. In order to prevent that, the DataReaders can be
configured to sense for a carrier (transmission of another DataReader or
DataSeal) before they start transmitting. When a DataReader is configured
for Carrier Sense, each time before it transmits something it listens to the
frequency, and only if it's clear (no one else is transmitting), it start
transmitt ing it s own message.
6. Burst Re cei vin g Mode
When DataSeals are operating in Alert Burst mode, the DataReader’s
receiver must be ON at all times in order to receive the Burst messages.
The controlling computer has to query the DataReader periodically to
receive the Burst messages that the DataReader received.