System information

Installing Hardware Options
VAX 4000 Model 108 User Information
3–19
Asynchronous Communication Options
The VAX 4000 108 system supports two different asynchronous communications options.
These options are as follows:
• DHW42-BB -- This asynchronous option provides 16 asynchronous DEC423 data-
line-only communications lines through two system ports. You can connect up to 16
peripherals using the MMJ ports on two harmonicas (H3104) that connect to the
option cables (BC16C-10).
Use the following cables instead of the BC16C-10 cable if you require longer cable
lengths: BC16C-25, BC16C-50, BC16C-A0, or BC16C-B5. Use the following cables
between the harmonica (H3104) and the DEC423 peripheral: BC16E-10, BC16E-25,
or BC16E-50.
• DHW42-CB -- This asynchronous option provides eight asynchronous EIA-232
modem control lines through two system ports using two breakout cables (BC29J-06).
Attach one of the following cables to a connector on the breakout cable if you require
longer cable lengths: BC22F-10, BC22F-25, or BC22F-50. The peripheral you are using
may require a null-modem extension cable. See the peripheral documentation or contact
your Digital sales representative for information on the correct null-modem cable to use.
Installing the Asynchronous Communication Option
The VAX 4000 108 system supports two different asynchronous communications options,
DHW42-BB and DHW42-CB in the top slot of the I/O receiver. To install either of these,
follow these instructions:
1. Turn off the system, unplug the power cord and remove the cover.
2. Insert the module into the top slot of the I/O receiver, pressing it firmly into place
to seat the connection.