Instruction manual

Control over the Main
Link Modems
The control of the dial-up modems serving the main link is made by means of the
DTR line of the DV-MUX3 main link interface. Assuming that the modems were
configured as explained above, the sequence for setting up and for disconnecting
the link between two DV-MUX3 units is as follows:
• The link is in the disconnected state when no user traffic is present. Both
DV-MUX3 units monitor the state of the RI line in their main link interface.
• When a voice channel at either the master or the slave DV-MUX3 is acti-
vated (see previous section), or the DTR line in the data channel interface of
the slave DV-MUX3 is asserted, the corresponding DV-MUX3 asserts the
DTR line in the main link interface. This causes the modem to dial the
number preprogrammed by the user.
• When the remote DV-MUX3 senses the assertion of the RI line in its main
link interface (indication of incoming call provided by the dial-up modem),
it asserts the DTR and RTS lines in its main link interface, and tries to syn-
chronize to the other DV-MUX3.
• In case the DV-MUX3 does not synchronize within 40 seconds, it switches
the DTR line OFF. If a request for connection is still present, the DV-MUX3
returns the DTR line to ON after 100 msec. This interval is sufficient for the
modem to disconnect, and then to start a new dialing attempt.
• When the two DV-MUX3 synchronize, they assert the CD and CTS lines in
the data channel interfaces.
• Normally, the disconnection of the link is initiated by the slave DV-MUX3,
after 25 seconds during which both voice channels are inactive and the DTR
line in the slave data channel interface is OFF continuously. To disconnect,
the slave DV-MUX3 switches the DTR line in the main link interface OFF.
This causes the slave modem to go on-hook.
In case the master DV-MUX3 senses a loss of synchronization condition for
two seconds, the master DV-MUX3 switches the DTR line in the main link
interface OFF. This causes the master side modem to go on-hook.
System Bandwidth
Utilization
Tables 1-1 and 1-2 list the bandwidth available to the DV-MUX3 data channel as
a function of the number and digitizing rate of the voice channels:
• Table 1-1 provides the data channel bandwidths for the adaptive and non-adap-
tive 1 modes. Under
Idle Voice Channels, you will find the bandwidth available,
in the adaptive mode, for the data channel when both voice channels are idle.
• Table 1-2 provides the bandwidths for the non-adaptive 2 mode (this mode
is intended for equipment limited to operation at standard data rates).
TYPICAL APPLICATIONS AND SYSTEM DESIGN CONSIDERATIONS
DV-MUX3 Installation and Operation Manual 1-11