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Model BB-422LCON, RS-232 to RS-422 converter, converts unbalanced
RS-232 signals to balanced RS-422 signals. The RS-422 Standard uses a
balanced voltage digital interface to allow communications of 90K bits per
second on cable lengths of 1200 meters (4000 ft). Ten receivers can be
connected to any one driver for use in multi-drop systems.
The RS-232 port is a male DB-25 connector with pins 2 (TD input) and 3 (RD
output) supported. Protective Ground (pin 1) and Signal Ground (pin 7) are
also connected. The RS-422 port uses a female DB-25 type of connector
with the Send Data outputs on pins 2 and 14, and the Receive Data inputs
on pins 5 and 17. Protective Ground (pin 1) and Signal Ground (pin 7) are
connected through to the RS-232 connector.
Interconnection of the converter with another RS-422 device:
The polarity of the two RS-422 lines must be correct. With no data being sent
the RS-232 line should be negative and the RS-422 “A” terminal should be
negative with respect to the “B” terminal.
The RS-422 Standard wire recommended is number 24 AWG copper
conductor, twisted-pair telephone cable with a shunt capacitance of 16 pF
per foot.
For long runs and/or high data rates, it is recommended that the wires be
terminated with a resistor at the receive end. The twisted pair usually used
has an impedance of about 100 Ohms, therefore a 100 Ohm resistor is
normally used for the termination. The RS-422 side of the converter requires
more power as the transmission line is increased and as the termination
resistor value is reduced, therefore it may be necessary to use a termination
resistor that is greater than 100 Ohms.
The RS-422 driver has the ability to drive ten RS-422 receivers connected
in parallel. A system of multiple receivers may require some experimentation
with location and size of termination resistors, line lengths, grounding, etc.
The RS-422 Standard recommends that Protective Ground (pin 1) be
connected to a good “green wire” ground. This may be already connected
in your RS-232 equipment. Protective Ground and Signal Ground should
be connected through to each end of the system and be connected to each
other using a 100 Ohm 1/2 Watt resistor at one end only. If a shielded twisted
pair is used the shield be connected to Protective Ground.
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General
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Mounting
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Power
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Serial Type
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Technology
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Features
- Converts unbalanced RS-232 signals to balanced RS-422 signals
- Data rates up to 90 kbps
- Extends RS-232 line up to 1200 meters (4000 ft)
- RS-422 driver can drive ten RS-422 receivers in parallel (for use in multidrop systems)
- Power supply required (not included, sold separately)
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