Receiving A Dialed Call From An X.21 Dce - PictureTel Concorde 4500 Servicing Manual

Receiving a Dialed Call from an X.21 DCE

This section describes the sequence of events that occurs when the
far-end videoconferencing system and the DCE initiate a dialed call
and later disconnect the call.
1. When the DCE detects an incoming call, it notifies the Concorde 4500
by sending at least two SYN characters followed by a string of BEL
characters on the R signal.
2. When the Concorde•4500 answers, it asserts the C signal. The
Concorde•4500 answers automatically or manually, depending on
whether it is in Auto Answer or Manual Answer mode.
3. When the DCE detects that the Concorde•4500 has answered, the DCE
may send DCE-provided information that can indicate details such as
charges, date, time, and the type of call.
4. When the connection is established, the DCE notifies the
Concorde•4500 that the DCE is ready to transfer data by setting the R
signal to binary 1 and asserting its I signal. Both the Concorde• 4500
and the DCE begin transferring their data.
5. When the DCE detects that the far end is disconnecting, the DCE sends
a clear indication by deasserting its I signal and placing binary 0 on its
R signal. The Concorde•4500 responds by deasserting its C signal and
placing binary 0 on its T signal.
6. The DCE and the Concorde•4500 return to the Ready state by placing
binary 1 on the T and R signals.
In Auto Answer mode, the Concorde¥4500 automatically
F.Y.I.
F Y I
answers a call within 500 milliseconds. In Manual Answer
mode, a call is answered when it receives a signal from the
keyboard.
X.21 Call Setup and Disconnect
3-17