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A1000 & A2000 USERS MANUAL 4
GENERAL DESCRIPTION
The A1000 and A2000 series converter boxes convert RS-232
communications signal levels to the correct electrical signals required by
RS-485. The RS-485 communications standard is recommended when
many modules, or other addressable devices, must be connected to a
host computer over long distances. The A1000 and A2000 converters
allow communications bus lengths up to 4,000 meters and baud rates up
to 115K baud using one twisted pair of wires.
The RS-485 communications standard is half-duplex, therefore data can
be transmitted in only one direction at a time. The A1000 and A2000
automatically control the bus direction without external handshaking
signals from the host. Therefore, host software written for RS-232 may be
used without modification. RS-485 bus control is completely transparent
to the user.
The A1000 and A2000 can also operate as RS-485 repeaters. Repeaters
are required to extend communications bus lengths or allow more than
32 RS-485 devices to be connected to a communications bus. A
repeater simply reamplifies, or boosts,
existing RS-485
signals
transmitted over long distances.
The A1000 converter boxes are powered by either 115Vac or 230Vac
and contain an internal +24-volt 1A power supply for powering modules.
The A1000 power supply is protected against overloads and short
circuits. The internal power supply may be used to power accessory
circuits such as relays or 4-20mA transmitters. The A2000 converter
boxes operate on a wide range of power supply input voltage:+10 to
+30Vdc unregulated.
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