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Signaling Function
Figure 3-4
DS0
Ring to Ground
Loop still closed
Dial tone
Digits
On-hook
Note
Figure 3-4
many more messages between the local and remote call agents and the local and remote VISMs.
Refer to the
The call processing for the VoIP switching and switched AAL2 operating modes is described in the
following list:
The call agent requests VISM to look for an off-hook signal when the line is idle.
1.
Upon receipt of an on-hook signal, VISM starts a timer and checks later to ensure that the line is
2.
still off-hook.
3.
VISM notifies the call agent that the caller has gone off-hook (this timer mechanism is also used
when processing on-hook/off-hook signaling to determine flash-hook events).
When the call agent is informed that the user is off-hook, the call agent instructs VISM to generate
4.
dial tone and to look for dialed digits.
Cisco VISM Installation and Configuration Guide
3-8
CAS Signaling in Initiating and Terminating a Call
Start Timer
Clear Timer
CALL IN PROGRESS
shows only the local CAS aspects of call setup. The entire process of call setup involves
"Call Control Function" section on page 3-15
VISM
Notification Request, (off hook)
Ack
VISM
Notify Message, (off hook)
Notification Request (dial tone,
digit collect, on-hook)
Notify Message (digit string)
Connect
Notify Message, (on-hook)
Delete Connection
for more information.
Release 3.0, Part Number OL-2521-01 Rev. D0, June 2004
Chapter 3
VISM Functional Description
Call Agent
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