Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

Chapter 1 29
Introduction
Datacommunications and Terminal Subsystem (DTS)
Local Area Network
HP 2345B Datacommunications and Terminal Controllers are
connected to the system via a Local Area Network (LAN) connection,
over coaxial cable which conforms to the IEEE 802.3 standard.
Hewlett-Packard provides two versions of this cable, ThinLAN and
ThickLAN, each of which provides certain specific advantages to the
user.
Each DTC has a unique LAN address, also referred to as the node
address or the station address, which serves to identify the DTC as a
node on the LAN. You should keep in mind, however, that while DTCs
are treated as nodes for purposes of configuration, they are not true
nodes in the sense that nodes are normally defined. DTCs are dedicated
communication devices; they are not self-contained, general-purpose
computer systems.
LAN Interface Card (LANIC)
Every computer in the HP 3000 Series 900 family of computers includes
a LAN Interface Card (LANIC) as part of its basic hardware. This
card is located in the System Processing Unit (SPU) and enables the
system to communicate with asynchronous devices via the LAN by
providing the basic connection between the computer and the LAN.
ThinLAN Connection
Two versions of LAN cable are available. The first version, ThinLAN
(Type 10BASE2), is available in connection lengths of up to 185 meters
(555 feet), and supports up to 30 nodes. ThinLAN provides an
economical solution where DTCs are located fairly close to their
associated computer systems. ThinLAN cable is very flexible and easy
to install, and can be bent around objects to accommodate its use in
confined areas. The ThinLAN is connected to each computer on the
LAN via a ThinMau (Medium Attachment Unit), with a small BNC
T-connector used to connect each DTC to the LAN. (Note that the
ThinMAU for the DTC itself is built into the DTC box.) You can connect
up to three segments of the ThinLAN cable with two repeaters, thus
extending the length of the LAN to 555 meters. Figure 1-3 depicts a
configuration using ThinLAN.