When a large number of readers are operating in the same area - for example four controllers, each with two antennas operating in a 10 square metre area - you can experience something called 'crosstalk' is when several readers talk at the same time. The noisy environment makes it harder to hear tag responses and typically results in degraded performance. Examples of poor performance would be diminished range, slow response times and even no response. It is like trying to have a conversation in a crowded pub. You cannot always hear what the other person is saying and you are never sure if you are being heard above the crowded noise.
As a result, reader manufacturers have developed different ways of dealing with the noise of several readers talking at the same time. One method is called 'Listen-Before-Talk'. That means a reader listens for another reader's transmissions before it starts its own. It is similar to being polite in conversation. I do not start talking until you have finished your sentence. Another approach is synchronisation whereby readers transmit at different intervals, this results in only one reader transmitting at a time thereby eliminating noise.
It is important to be aware of crosstalk typically where there are two different systems running within close proximity to one another.
For more information contact Nigel Graham, Dortech, 031 700 8260, nigel@dortech.co.za
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