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Modem Signal and Line States
Signal and Line State Diagrams
DC-158
Cisco IOS Dial Technologies Configuration Guide
The diagrams show two processes:
• The “create daemon” process creates a tty daemon that handles the incoming network connection.
• The “create EXEC” process creates the process that interprets user commands. (See Figure 25
through Figure 29.)
In the diagrams, the current signal state and the signal the line is watching are listed inside each box.
The state of the line (as displayed by the show line EXEC command) is listed next to the box. Events
that change that state appear in italics along the event path, and actions that the software performs are
described within ovals.
Figure 25 illustrates line states when no modem control is set. The DTR output is always high, and CTS
and RING are completely ignored. The Cisco IOS software starts an EXEC session when the user types
the activation character. Incoming TCP connections occur instantly if the line is not in use and can be
closed only by the remote host.
Figure 25 EXEC and Daemon Creation on a Line with No Modem Control
Ringing
Ready
Exit
Create
daemon
Network
c
onnection
closed
Incoming
network
connection
Ready and active
DTR high
Ready and active
User-typed
activation
character
Create
EXEC
DTR high
S1201a
DTR high