B&B Electronics 4WSD25OTB - Datasheet - Manual (Page 3)

P#9150_4WSDxxOTB-0812ds - p3/4
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Figure 1: 2-Wire RS-485
Used to connect several RS-485
devices with minimal wire.
Devices communicate one at a time.
Units are normally in receive mode.
When data is requested, the
addressed device waits one delay
time before responding.
After transmitting, the device reverts
to receive.
Switch settings are: Switch 1: RS-
485, Switch 2: Echo Off, Switches 3
and 4 to 2-Wire.
Figure 2: 4-Wire RS-485
Used for 4-Wire Master/Slave
circuits.
Each device is polled, allowing
faster response time.
Addressed devices can receive
while responding to a request.
When used as a Master in a single
master system, Switch 1 may be
set RS-422 since it is the only
transmitter.
When used as a slave, the RS-232
device must provide addressability.
Select RS-485 mode in this
situation.
Biasing is provided by the end-of-line slave.
Switch settings for this mode are : Switch 1:
RS-485, Switch 2: Echo On, Switches 3 and
4: 4-wire.