Composite Links; Multiplexer Configuration - Digital Equipment MUXserver 100 Reference Manual

1.3.2 Composite Links
The 'composite link' is the communications mechanism between the DECmux
II and the MUXserver 100 or between two DECmux II units. The composite
link may use the Public Data Network and, as such, will be configured as an
RS-232 synchronous link by means of modems. Short haul links not using the
Public Data Network can be configured as either Synchronous RS-232 Null
Modem lines (for distances less than 50 feet (15 meters)) or as Synchronous
RS-422 long line driver connections (for distances less than 3280 feet (1 ki-
lometer)). In either configuration, the composite link is transparent to the re-
mote asynchronous terminal user. Link speeds ranging from 1200 baud to 19.2
K baud are selectable for RS-232-C, with up to 38.4 K baud for RS-422.
1.3.3 Multiplexer Configuration
Figure 1-3 and Figure 1-4 show the default configurations available on the
MUXserver 100. The MUXserver 100 determines which configuration is used
by monitoring the 'composite link' connections at power up. Both Figure 1-3
and Figure 1-4 show the composite links being provided as RS-232 MODEM
connections, which are the Default Factory Settings. To change any of the
composite links to RS-422 or to vary link speed, the MUXserver 100 and each
DECmux II unit must be individually set up. See Chapter 2, Section 2.5
(SETTING UP THE COMPOSITE LINK PARAMETERS).
The maximum multiplexer configuration supported by the MUXserver 100 is
two DECmux II units giving a total of 16 remote asynchronous terminals. A
partial configuration consisting of only one DECmux II (eight remote terminals)
connected to either Port A or Port B of the MUXserver 100 is also valid.
The choice of multiplexer configuration greatly depends on the geographic loca-
tion of the remote users. Some factors which may influence the selection are:
1. If all 16 remote users are at one site, Figure 1-4 should be used with
the composite link between the two DECmux II units being either
RS-232 Null Modem (for distances less than 50 feet (15 meters)) or
RS-422 long line drive (for distances less than 3280 feet (1 kilome-
ter)). This provides the least cost implementation avoiding additional
modems, leased lines, and so on.
2. For separate remote sites, where MODEM connections are required
for each conlposite link, Figure 1-3 is recommended. This ensures the
best response time for users by limiting the number of asynchronous
channels multiplexed on anyone composite link to eight.
CHAPTEFr 1 THE MUXserver 100 ENVIRONMENT 5