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Modem Signal and Line States
This chapter describes modem states in the following section:
• Signal and Line State Diagrams
To identify the hardware platform or software image information associated with a feature, use the
Feature Navigator on Cisco.com to search for information about the feature or refer to the software
release notes for a specific release. For more information, see the “Identifying Supported Platforms”
section in the “Using Cisco IOS Software” chapter.
For a complete des
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Modem Signal and Line States Signal and Line State Diagrams 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
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Modem Signal and Line States Signal and Line State Diagrams Configuring Automatic Dialing With the dialup capability, you can set a modem to dial the phone number of a remote router automatically. This feature offers cost savings because phone line connections are made only when they are needed—you pay for using the phone line only when there is data to be received or sent. To configure a line for automatic dialing, use the following command in line configuration mode: Command Purpose Route
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Modem Signal and Line States Signal and Line State Diagrams Figure 26 EXEC Creation on a Line Configured for a High-Speed Modem Idle state DTR low, watching CTS Ring transition Raise DTR Lower DTR Answer timeout DTR high, DTR low Hang up watching Ringing CTS Lower DTR close connection CTS raised Create EXEC CTS lowered or exit DTR high Ready and active Supporting Dial-In and Dial-Out Connections To configure a line for both incoming and outgoing calls, use the following command in line co
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Modem Signal and Line States Signal and Line State Diagrams Figure 27 EXEC and Daemon Creation for Incoming and Outgoing Calls Idle state DTR high, watching CTS CTS raised Close connection, DTR low for 5 seconds CTS lowered DTR high, DTR going Hang up watching Ready low CTS User-typed Incoming network activation connection Create character EXEC Create daemon Ready DTR high, Ready DTR high, and watching and watching active CTS CTS active CTS lowered CTS lowered or or exit network connect
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Modem Signal and Line States Signal and Line State Diagrams Closing Modem Connections Note The modem cts-required command was replaced by the modem printer command in Cisco IOS Release 12.2. To configure a line to close connections from a user’s terminal when the terminal is turned off and to prevent inbound connections to devices that are out of service, use the following command in line configuration mode: Command Purpose Router(config-line)# modem cts-required Configures a line to close
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Modem Signal and Line States Signal and Line State Diagrams Configuring a Line to Disconnect Automatically To configure automatic line disconnect, use the following command in line configuration mode: Command Purpose Router(config-line)# autohangup Configures automatic line disconnect. The autohangup command causes the EXEC facility to issue the exit command when the last connection closes. This feature is useful for UNIX-to-UNIX copy program (UUCP) applications because UUCP scripts cannot
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Modem Signal and Line States Signal and Line State Diagrams Figure 29 Daemon Creation on a Line Configured for Modem Dial-Out Idle state DTR low Incoming network connection Raise DTR Lower DTR Answer timeout DTR high, watching Ringing CTS Close connection CTS raised Lower DTR Network connection closed or Create daemon CTS lowered DTR high, watching CTS Ready and active Cisco IOS Dial Technologies Configuration Guide DC-164 S1930
