PictureTel Concorde 4500 Servicing Manual page 85

4. When the DCE detects the + character from the Concorde•4500, it
stops sending + characters to the Concorde•4500 and starts dialing the
number requested, and may send call progress signals to the
Concorde•4500. Call progress information identifies events such as
dialing and ringing.
5. The DCE follows the call progress information with information that can
indicate details such as charges, date and time, and type of call.
6. When the connection is established, the DCE asserts (on) the I signal,
thus notifying the Concorde•4500 that the DCE is ready to transfer data.
Both the Concorde•4500 and the DCE transfer their data.
7. The Concorde•4500 indicates a clear request to the DCE by
deasserting its C signal and placing binary 0 on its T signal. The DCE
confirms the clear request by deasserting its I signal and placing binary
0 on its R signal. Then the Concorde•4500 and the DCE return to the
Ready state by setting the T and R signals to binary 1.
The following illustration describes what takes place when a dialed
call is placed using the X.21 network interface.
X.21 Call Setup and Disconnect
3-15