• The B400X expander provides ten additional Q–bus slots for a system total
of 17 Q–bus slots. The B400X also has space for up to four additional EF
/RF-series ISEs or up to three ISEs and a tape drive (TF-series, TK50, or
TK70).
Note
Using the dual-disk RF (available with the R400X and B400X expanders)
you can increase the number of ISEs, up to seven per DSSI bus.
• The SF12 expander box provides for up to four RF-series devices.
• The SF100 storage array pedestal provides space for a TF857 magazine tape
subsystem and one SF-series storage array building block.
• The SF200 storage array subsystem provides space for up to two TF857
magazine tape subsystems and up to six SF-series storage array building
blocks.
Contact your Digital representative for more information on those and other
expander products.
1.2.2.4 Communication Controllers
Besides the console serial line, most systems have additional communication
controllers for connecting additional terminals and for communicating with other
systems over telephone or network lines. Such controllers provide standard
interfaces between peripheral devices and the system, and many provide support
for multiple data lines.
The following types of communication controllers are available.
• Asynchronous serial controllers
• Synchronous serial controllers
• DECservers
• Network controllers
Asynchronous Serial Controllers
Asynchronous serial controllers provide low-speed connections between peripheral
devices and a system. Asynchronous communication between the system and its
peripheral devices depends on recognition of a pattern of start and stop bits, not
on a time interval.
System Overview 1–25
