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programming of the data port from the DTE keyboard, the DTE must be on-line (for
instance, by setting the CT108 signal of the data port on).
The microprocessor of the DCE prompts the DTE for input that can be dial information
or a special command to enter programming mode. If keyboard dialling is selected then a
number or name can be entered for dialling. If V.25 bis or AT-command dialling is selected,
the microprocessor interprets the entered call set-up request and returns the result to the
terminal.
After the entry of dial information the microprocessor uses the D-channel protocol to
send the dial information towards the ISPBX. After the destination party has answered the
call, the data rate adaptor starts sending and receiving the frame pattern. After
synchronisation the microprocessor connects the DTE to the data rate adaptor and the
transparent DTE-DTE connection is established. If the user transmission rate is 64 kbps
no synchronisation phase is necessary and the terminal is switched to the data rate adaptor
when the opposite party has answered.
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ISPBX initiates activity.
The microprocessor of the DCE is able to communicate with the CPU using D-channel
messages. If an idle data party is called, the microprocessor receives a call set-up message.
If required, the calling party identification (part of the call set-up message) can be sent to
the DTE.
The incoming call can be answered automatically (DCE answers the call autonomously) or
manually (DTE answers the call). The data rate adaptor starts sending and receiving the
frame pattern. After synchronisation the microprocessor connects the DTE to the data
rate adaptor and the transparent DTE-DTE connection is established. If the user
transmission rate is 64 kbps no synchronisation phase is necessary and the terminal is
switched to the data rate adaptor when the opposite party has answered.
Note: If the data port supports synchronous communication, this only applies to the user - user
data transfer phase. The communication between the DTE and the DCE is asynchronous
and is used for programming and dialling the destination number. After the connection has
been set-up to the destination DTE the transmission mode can be switched over to
synchronous communication. If the DTE is not able to perform the switch-over the
connection set-up can be performed automatically using the hot line facility.
A schematic overview of the data port configuration and its place in the SOPHO-SET,
SOPHO-LAM or LAM is illustrated in the following figures.
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