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11
Chapter 1 - Introduction and Description
communications software to the DATA/COMMAND connector on the back panel and configure
the data channel for the type of data that is going to be transferred. For example, if an
asynchronous device is going to be connected to the data channel, you must set the speed of the
channel, the word length, the number of stop bits, whether or not you are going to have parity
checking, the flow control type, and other aspects of asynchronous data. After you have
configured the data channel, remove the command port device and connect the data channel
device, allowing data to be transferred from the asynchronous device to the MultiMux’s input/
output circuitry.
To operate the data channel in synchronous mode, as when connecting to a remote LAN bridge
or to the composite link of an MMH900 series MultiMux, use the same DATA/COMMAND
connector. The sync device you connect to the data channel must be an SLDC or HDLC device.
Configure the data channel for sync channel operation with any SLDC/HDLC protocol , for
internal or external clocking, and for speed. Configuration information is stored in non-volatile
memory, which informs the data/command processor how data is received from the input/output
(I/O) circuitry.
To set up the DataTalker for voice or fax operation, connect the VOICE/FAX CHANNEL 1 FXS
connector on the back panel to a telephone or fax machine, connect the FXO connector to a PBX
station circuit, or connect the E&M connector to a PBX E&M trunk. The FXS (Foreign eXchange
Station) circuitry in the DataTalker allows a telephone or fax machine to be directly connected to
the DataTalker. This circuitry provides a ringing voltage to the remote instrument when it detects
an off-hook condition from the attached device, so that when two telephones are used, picking up
one of the handsets rings the telephone at the other end. If the FXO (Foreign eXchange Office)
connection is used at one end of the network and a telephone set is used at the other end of the
network, the PBX provides the dial tone, and the remote user can dial a number as if locally
attached to the PBX. The E&M connector is used to link two PBXs.
Before a voice or fax operation can take place, the DataTalker must be configured for the types of
local and remote connections and for the line conditioning for the voice circuitry. The voice/fax
channel is configured in the same way as the data channel: by connecting a command port
device to the DATA/COMMAND connector on the back panel and setting the voice/fax
configurations. Once the channel is configured, the analog to digital conversion circuitry accepts
the incoming analog signal and converts it to a digital representation of the signal. The digitized
signal is stored in the dual-port RAM for transmission to the serial communications controller
when it requests the dual-port RAM for data. The serial communications controller conditions the
digitized voice or fax data for transmission to the composite link.
In order to transfer data from the serial communications controller over the composite link to the
remote site, the composite link must be configured. Factors to be considered include whether an
external device or an internal modem, DSU, or terminal adapter or installed, the speed of the link,
who is providing the clocking, and other link conditioning factors. The composite link is
configured using a command port device and menus the same way we configured the data and
voice/fax channels. This is accomplished by setting the link configurations to match the link
device installed in the DataTalker and the requirements of the link service and remote system. If,
for example, an internal DSU is installed that will be connected to a DDS network that provides
clocking, the DataTalker detects that the link device is an internal DSU. Through the configuration
stored in nonvolatile memory, it knows that the clocking is going to be provided by the DDS
network. When you look at the versatility of the composite link, many other factors must be
considered, such as answer or originate, two- or four-wire, and dial-up or leased line operation.
But all these considerations are handled in the same manner as the example of the DSU above.
This is basically how your DataTalker is connected to a data device and voice or fax equipment,
how the internal logic is conditioned to transfer data, and how the composite link passes that data
on to the remote site.