Lexmark 33S0300 - Mono Chrome Laser Printer Reference page 337

The following illustration shows the pin assignments for the 9-pin to 25-pin IBM EIA
RS-232C serial cables.
Serial Communication Parameters (RS-232C)
The following paragraphs show acceptable values for serial communication
parameters.
Voltage Level Range
The maximum voltage level for control lines or data lines is +/- 25 positive V dc and
+/- 25 negative V dc. A timing or control line is active if the voltage is more than +3 V,
or inactive if the voltage is less than -3 V. The voltage reference point is the signal
ground on pin 7.
A data signal greater than +3 V means that the bit is a logical 0. A signal less than
-3 V means that the bit is logical 1.
For additional information, refer to Interface between Data Terminal Equipment and
Data Communications Equipment Employing Serial Binary Data Interchange,
published by the Electronic Industries Association, publications EIA RS-232C and
EIA\TIA-232-E.
9 to 25 Pin Cable Adapter,
such as IBM 6450242 (10 in.)
Shield
9 (F) 25 (M)
8-23
Lexmark 1038693 (50 ft)
Shield
25 (F)
Interfaces
25 (M)