Call Setup And Disconnect; Placing A Dialed Call With X.21 Data Circuit-Terminating Equipment (Dce) - PictureTel Concorde 4500 Servicing Manual

NETWORK INTERFACES
X.21 Call Setup
and Disconnect
F Y I
Placing a Dialed Call with X.21 Data Circuit-Terminating
Equipment (DCE)
3-14
When a dialed call is disconnected from the near end:
The Concorde¥4500 deasserts the TR and RS signals.
The CSU deasserts the RR and CS signals.
Then the call disconnect is complete.
When a dialed call is disconnected from the far-end:
The CSU deasserts the RR and CS signals.
The Concorde¥4500 deasserts the TR and RS signals.
Then the call disconnect is complete.
This section describes the call setup and disconnect processes used
when the Concorde¥4500 has an X.21 network interface.
For the X.21 interface, there are two types of signals: control
F.Y.I.
signals and data signals. Control signals can be either in the
on or in the off state. Asserting places the signal into the on
state, and deasserting places the signal into the off state.
Data signals carry data and consist of strings of binary ones
and zeros.
This section describes the sequence of events that occurs when the
Concorde¥4500 initiates a dialed call and later disconnects the call.
1. The Concorde•4500 notifies the DCE (network) that it wants to make a
call by asserting its C signal and placing binary 0 on its T signal.
2. The DCE responds by sending at least two SYN characters followed by
a string of + characters on the R signal. This response signals the
Concorde•4500 to send the selection (dialing) information.
3. The Concorde•4500 sends the selection information, which consists of
at least two SYN characters followed by a string of IA5 (international
character set) characters and terminated with a + character. The IA5
characters provide the dialing information.