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RS-232↔485/422 CONVERTERS

Table 2 (continued). DTE Jumper Settings.

Function Jumper Requirements

9. RS-485 Interface Line Biased (Fail- S3 Off No line bias

Safe), Receive

S3 On Line biased

NOTE

If line bias is on, the RS-485 CD will ALWAYS be on.

3.3 Typical Applications

This section describes some typical applications where the RS-232↔485/422

Converter might be used. The connections shown in the figures are for the RS-485

port.

Figure 5 shows a typical point-to-point, 4-wire, full- or half-duplex connection with

both RS-232↔485/422 Converters terminated by setting switch S2 to the TERM

position. Figure 6 shows a typical point-to-point, 2-wire, half-duplex connection

with both RS-232↔485/422 Converters terminated by setting switch S2 to the

TERM position.

In a 4-wire, point-to-point application, each of the drivers on the two

RS-232↔485/422 Converters may always be enabled without any adverse effects.

In a 2-wire, point-to-point or multipoint application, only one driver may be

enabled at any one time. If more than one driver is turned ON, a situation known

as contention occurs and the data from one driver interferes with the data from

the other driver. This results in both sets of data being unintelligible.

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Plus RS-232 Spécifications Page 23