422OISPR4300 - pg. 1/2
B&B Electronics -- Revised November 2000
This product designed and manufactured in USA of domestic and imported parts by
Reversed RS-232 to RS-422 Optically Isolated Converter
With DB-25 Connectors & Surge Suppression
CE
CE
CE
CE
Model 422OISPR
The 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 for cable lengths
of 4000 feet. Ten receivers can be connected to any one driver for use in multi-drop systems.
The RS-232 port uses a female DB-25 connector with pins 2 (TD input) and 3 (RD output)
supported. Protective ground (pin 1) and Signal ground (pin 7) are connected through to the
RS-422 side of the converter. Neither of these two grounds is connected through to the RS-
422 side of the converter. Power for the RS-232 side of the isolated converter is taken from
the voltage, high or low, on the handshaking lines: pin 4 (RTS) and pin 20 (DTR). Pins 4 and 5 (CTS) are tied together. Pins 20, 6 (DSR), 8
(CD), and 20 are tied together.
The isolated RS-422 side of the converter has a male DB-25 connector to connect to the user's cables. Pin 2, TD (A), and pin 14, TD (B),
are the RS-422 output. Pin 5, RD (A), and pin 17, RD (B), are the RS-422 input. For the RS-422 side of the converter, twelve volts DC is
supplied through a power jack. A power supply is available from B&B Electronics. Surge suppression is provided for the RS-422 side across
TD (A), TD (B) and also across RD (A), RD (B). The surge suppressor is a 7.5 V, bi-directional avalanche breakdown device, with 500W peak
power dissipation and 1 picosecond (theoretical) clamping time. Surge suppressors add a maximum of 6000 picofarads.
Interconnection of the converter with another RS-422 device:
1.
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.
2.
The wire recommended in the RS-422 Standard is number 24 AWG copper conductor, twisted-pair telephone cable with a shunt
capacitance of 16pF per foot.
3.
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 has an impedance of about 100 ohms, therefore a 100 ohm resistor is normally used for the termination. In no case should the
termination resistor be less than 90 ohms.
4.
The RS-422 driver has the ability to drive 10 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.
To make the converter work:
1.
The RS-232 side of the converter derives its power from pins 2 (TD), 4, 5, 6, 8, and 20. This converter has been tested with all the RS-
232 power derived from pin 2, however, it is recommended that at least one additional handshake line be connected to the converter to
provide power for the RS-232 side of the converter. The voltage level that exists on the handshake line does not matter. The converter
will be able to derive power from the lines either in the positive or negative voltage state.
NOTE: When using an external supply, the supply should be connected only to specifically labeled power inputs (power jack,
terminal block, etc.). Connecting an external power supply to the handshake lines may damage the unit. Contact technical support
for more information on connecting an external power supply to the handshake lines.
2.
The RS-422 side of the converter must be connected to a 12VDC 100 mA power supply. A power jack is provided on the RS-422 side of
the converter to make this connection. To ensure proper isolation, the ground of the RS-422 side must not be connected to RS-232 side
of the Signal Ground (pin 7) on the RS-232 side of the converter.
DECLARATION OF CONFORMITY
Manufacturer's Name:
B&B Electronics Manufacturing Company
Manufacturer's Address:
P.O. Box 1040
707 Dayton Road
Ottawa, IL 61350 USA
Model Numbers:
422OISPR
Description:
Reversed Opt. Isolated RS-232/422 Converter
w/Surge Suppressors
Type:
Light industrial ITE equipment
Application of Council Directive: 89/336/EEC
Standards:
EN 50082-1 (IEC 801-2, IEC 801-3, IEC 801-4)
EN 50081-1 (EN 55022, IEC 1000-4-2)
EN 61000 (-4-2, -4-3, -4-4, -4-5, -4-6, -4-8, -4-11)
ENV 50204
EN 55024
Michael J. Fahrion, Director of Engineering
PDF 
ZIP