Model BB-422LCOR, non-isolated serial converter, converts unbalanced RS-232 signals to balanced voltage digital interface with data rates up to 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 female DB25 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 is a male DB25 connector with Send Data outputs on pins 2 and 14, and 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 wire recommended in the RS-422 Standard 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 termination. The RS-422 side of the converter requires more power as the transmission line is increased and termination resistor value is reduced, therefore it may be necessary to use a termination resistor that is larger 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.