HP 24SII - Manual (Page 40)

If you are interfacing a DTE device to the Model 24SII DES (DCE),
you must use a one-to-one or straight cable as shown in
Figure 5 on
the following page. If you are interfacing a DCE device to the Model
24SII DES (DCE), you must use a crossed cable as shown in
Figure 6
on the following page.
When using XON/XOFF protocol, it may be desirable to use cables
with only Tx, Rx and GND connected. On the serial ports of a
BayTech Model 24SII DES, input handshaking lines are enabled if
nothing is connected, allowing the system to operate with only Tx, Rx
and GND connected.
CAUTION: Do not attempt to use a serial cable on a parallel port.
Since an EIA-232 serial port usually carries a potential of +12 and -12
volts, plugging a serial cable from that port into a parallel port may
cause damage to the parallel port.