Instruction manual

• The second voice channel of the DV-MUX3 is used for PLAR service, and
is connected directly to the subscriber’s telephone set. This voice channel
uses an FXS interface.
• At the branch office, the two local subscriber sets are connected to the two voice
channels of the DV-MUX3. These voice channels use the FXS interface.
The first voice channel (connected at the main office to a subscriber line of
the PBX) is used for voice/fax transmission.
After the DV-MUX3 equipment is added, the data rate available to the SNA link de-
pendsonthemainlinkrateandtheselectedvoicebandwidth.Inthisexample,themain
link rate is 19.2 kbps; assuming the voice channels operate at 6.4 kbps, the guaranteed
bandwidth available to the SNA link decreases to 5.6 kbps (faster modems, e.g.,
28.8 kbps modems, would of course increase the guaranteed bandwidth).
However, the main advantage of using the DV-MUX3 in this application is the
availability of an adaptive mode: by using the DV-MUX3 adaptive mode, the de-
crease in the bandwidth would occur only when a voice channel is actually in use,
i.e., when someone makes a call: when the voicelines are idle, the bandwidth avail-
able to the SNA link is 18.4 kbps.
NOTE
IBM communication equipment uses the DSR line as an indi-
cation of channel activity. For such applications, an appropri-
ately wired cable must be used to connect the DSR line to the
DCD line of the DV-MUX3 data channel connector.
Note that theDSR line is supported only for the RS-232 interface.
Typical DV-MUX3
Application in an
Inter-LAN Link
Figure 1-2 shows another typical application for a DV-MUX3. In this example, the
DV-MUX3 is used to provide two telephone channels between the branch offices
and the main offices by sharing an already existing data link. This link is used by
a pair of remote Ethernet bridges or routers that interconnect the LANs serving the
main and branch offices. The DV-MUX3 is inserted between the remote bridges
and the data link, in a way similar to that shown in figure 1-1.
Other Applications The adaptive mode of the DV-MUX3 also can be used when the available main
link bandwidth is shared with statistical multiplexers, or with any other type of
equipment that can run at the rate of the clock signals supplied to it. This issue is
further explained in the System Timing Considerations section.
Dial-up Mode The dial-up mode (available only when the main link interface is RS-232 or V.35)
allows the use of a switched PSTN line to connect between two DV-MUX3 units,
thereby reducing the operating cost as the line is used only on demand.
The dial-up mode requires the use of the master-slave configuration. For proper
operation, the DV-MUX3 installed at the central location must be defined as the
master, and the other DV-MUX3 must be defined as the slave.
Conditions for
Activation/Deactivation
of a Voice Channel
The DV-MUX3 interprets the following conditions as a request from a voice chan-
nel for the connection of the link to the remote DV-MUX3:
• For a voice channel with FXS interface: the detection of an off-hook con-
dition at the voice channel interface.
CHAPTER 1 - INTRODUCTION
1-8 DV-MUX3 Installation and Operation Manual