8
v3.0 AB
What Is RS-232?
A minimal "3-wire" RS-232 connection consisting only of transmit data, receive data, and
ground, is commonly used when the full facilities of RS-232 are not required. The RS-232
standard defines the voltage levels that correspond to logical one and logical zero levels for the
data transmission and the control signal lines. Valid signals are either in the range of +3 to +15
volts or the range −3 to −15 volts with respect to the "Common Ground" (GND) pin; consequently,
the range between −3 to +3 volts
is not a valid RS-232 level.
Typical 3 wire RS-232 connection. A cable can be made with one end as shown below and
the other connected to the TX, RX, and GND on the Digital U
-
Type. Note: TX on one side will
connect to RX on the other side and vice versa. An RS-
232 to USB adapter can be used as well.
The Female DE-9 connector is the mirror image of the Male DE-9 connector. These diagrams show the
connectors face-on.
