7: Synchronous Dce Configuration; Connection Types; Nailed-Up Connections; Circuit Switched Connections (Cs) - AT&T 7500 User Manual

CHAPTER 7: SYNCHRONOUS DCE CONFIGURATION
The 7500 in the synchronous configuration is used for synchronous data transfer. In synchronous
operation, all options are set from the front panel on the 7500. The 7500 can also originate data calls,
answer incoming data calls, and disconnect data calls from the front panel.

Connection Types

The 7500 in the synchronous configuration can have either a nailed-up connection, a circuit
switched connection (dialed up or permanent switched connection), or an On-Demand B-channel X.25
connection.

Nailed-Up Connections

If you have set the Mode option for nailed B1 or nailed B2, the 7500 transfers data between the
EIA-232D or V.35 interface and the specified channel (B1 or B2) regardless of any signaling for control
of the channel. One application for this type of connection is to interface an external PAD/Multiplexer
directly with the 5ESS X.25 packet switch.

Circuit Switched Connections (CS)

If you have set the Mode for circuit switched (CS), data calls are established and disconnected at
the user's discretion, except that permanent switched connections are established automatically by the
switch.
On-Demand B-Channel X.25 Connections (BX Local and BX Remote)
An On-Demand B-Channel X.25 connection is a special form of a circuit switched connection which
is used exclusively for a B-Channel connection to an X.25 packet switch. Selection of BX Local is
appropriate for establishing a B-Channel X.25 connection to the local X.25 packet switch, e.g., the 5ESS
switch, while selection of BX Remote is appropriate for connection to a packet switch external to the
5ESS switch. BX Local operation requires that a null telephone number be dialed (analogous to a hot
line call; see CHAPTER 3: FRONT PANEL FEATURES ACCESS, the section on dialing an unstored
number).

Making a Data Call

You can make a data call from the front panel of the 7500 as described in CHAPTER 3: FRONT
PANEL FEATURE ACCESS. You can also make a data call using the Autodial option or the
Multipurpose Enhancement Board RS-366 (see the REFERENCE chapter).
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