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Your modem will hang up and return to local command state if your computer
transmits characters while the modem is attempting to establish or re-establish a
connection (unless &N0 has been issued).
Auto Leased Line Operation (&L2 or &L3)
You can select Auto leased line operation with the &L2 or &L3 command. In Auto leased line
operation you do not need to issue the ATA command to answer a call, or the ATD command to
initiate a call. Issue the &L2 command to automatically select Originate mode, or the &L3
command to automatically select Answer mode.
In Auto leased line operation AT commands can only be entered while DTR is low. Irrespective
of the &D setting, your modem will remain in idle mode when DTR is low, and will go on-line
when DTR is high and the modem’s TALK/DATA switch is set to DATA. If DTR is lowered
(or the TALK/
DATA switch is set to TALK) when your modem is on-line, it will hang up and return to idle
mode. If power is lost, your modem will enter on-line state when DTR is restored.
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Your communications software must be capable of altering the state of the DTR
signal to work successfully with the &L2 and &L3 commands.
If your modem has a TALK/DATA switch, it must be set to DATA.
Hanging Up
There are four ways of hanging up your modem when leased-line mode is selected.
❏ If your modem is attempting to establish or re-establish a connection, sending characters to it
will cause it to hang up (unless &N0 has been issued).
❏ If synchronous mode is selected, lowering the DTR signal will cause your modem to
immediately hang up.
❏ If asynchronous mode is selected, issuing the ATH command will cause the modem to hang
up.
❏ If asynchronous mode is selected (&L2 or &L3), lowering DTR will cause the modem to
hang up.
❏ Switch the TALK/DATA switch to TALK.
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XON/XOFF flow control should not be selected for leased-line connections. Your
modem will prematurely hang up if your computer sends an XON/XOFF character
while the modem is attempting to reestablish a connection.
Improving the Reliability of Leased-Line Connections If you are experiencing data errors over
leased lines, issue the %L command to lower the transmit level of your modem. You may need to
experiment with the levels, but start between %L15 and %L19.
The transmit level should be changed on both modems.