How is this RS485 module working?

I am using an RS485 module :- http://www.elecrow.com/uart-ttl-to-rs485-twoway-converter-p-1545.html

This module is bidirectional and uses a single pair of differential signal to transmit/receive data. My question is how is the chip deciding whether it has to transmit data from TX to A+ B- or from A+ B- to RX?. Shouldn't there be 2 pairs of differential signal, one pair for TX and the other pair for RX? What is happening in this module??

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0 COMPACT over 8 years ago

RS485 uses 4 wires for unrestricted full-duplex mode.
However just two wires can be used for half-duplex mode between two nodes which can be made to appear as a (slower) full duplex connection to their hosts.
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0 COMPACT over 8 years ago

RS485 uses 4 wires for unrestricted full-duplex mode.
However just two wires can be used for half-duplex mode between two nodes which can be made to appear as a (slower) full duplex connection to their hosts.
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