The 3220-series Auto Parallel Switches are electronic data switches which support Bi-Directional
Centronics Parallel data transmission, including IEEE-1284 "nibble" mode.
This product allows multiple CPUs to share one parallel printer (or other parallel device)
without the need for manual selection or sharing.
Automatic input selection is on a first-come, first-served basis. When one user
is finished printing, the auto-switch waits for a period of time (adjustable from 5-60 seconds), then reverts
to polling all input ports for activity.
Port switching is transparent to all users, and there is no software required. As soon as
the printer port is cleared, the next waiting job will be passed through.
Special Note for Really Really Really Old Computers:
Most Bi-Tronics (BiDirectional) auto switches support the two
drivers HP LaserJet 5 provides, "Explorer" (under DOS) and
"Status Window" (under Windows 3.1), but are not suitable to
work in these two drivers.
In the old version of Explorer (provided with HP LaserJet 4),
the user has to request the printer status manually. In the
HP 5 version of Explorer and in Status Window, however, the
CPU requests the printer status automatically whenever it is
free; in case any odd situation occurs in the printer, it is
shown on the monitor right away.
If the 3220 Parallel Auto-Switch unit is in use with the new version of Explorer
or Status Window environment, two unexpected incidents will occur:
- When one PC is requesting the printer status, the
printer is occupied for about one second. In the
meantime, if another PC attempts to request the
printer status, its request will not be accepted.
Because this request is automatically performed by
the CPU, it will often happen that while a user is
using applications other than Explorer or Status
Window, the user will surprisingly get a message
on the monitor saying that the printer is offline
or that the cable is disconnected.
- When one PC is sending its print job, it occupies
the printer for a time. The other PC then gets a
message on the monitor saying that the printer is
off, or offline, or that the cable is disconnected.
The 3220 does support Explorer and Status Window, but
the above two situations are unavoidable when either of
these are active. Therefore, to avoid being disturbed by
these messages, we suggest you use the switch in applications
other than the newest versions of Explorer and Status Window.
To disable Explorer, comment out the STAT command in the
To disable Status Window, close the Status Window
application when in Windows.