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Chapter 5 – AT Commands, S-Registers, and Result Codes
Multi-Tech Systems, Inc. SocketModem MT5600SMI Developer’s Guide 49
Case 2: Telephone Line is in Use but Disconnected
If an ATDT, ATDP or ATDL is issued while Line-In-Use detection is
enabled and the telephone line is NOT in use, the modem will go off-
hook after a short pause, then respond with CONNECT or NO CARRIER
message.
Case 3: Telephone Line is not Connected to Modem
If an ATDT, ATDP, or ATDL is issued while Line-In-Use detection is
enabled and the telephone line is not connected, the modem will go off-
hook momentarily, go back on-hook, and then respond with NO DIAL
TONE message.
Extension Pick-up
(Enabled by AT-STE=2, AT-STE=3, AT-STE=6, or AT-STE=7):
Case 1: Modem off-hook, Local Handset Goes Off-Hook
If the local handset goes off-hook while the modem is in a data
connection, the local handset will be muted. The modem will then send a
GSTN Cleardown to the remote modem and then go on-hook. The
modem will then send a NO CARRIER message to the DTE. A result
code of 25 will be left in S86 register. After 2 seconds, the local handset
will be connected to the telephone line so the user hears the dial tone.
Remote Hang-up
(Enabled by AT-STE=4, AT-STE=5, AT-STE=6, or AT-STE=7):
Case 1: Modem off-hook, Remote Hang-up
If the modem is connected (off-hook) and the remote modem/server
goes hangs up, the central office may issue a line polarity reversal. If a
line polarity reversal is detected, the modem will drop the call and
respond with NO CARRIER. The reason for hang-up can be determined
by #UD or by S86=25. A line reversal can also be simulated by simply
pulling out the telephone line during a connection.
Operation in Voice Mode
Line-In-Use
(Enabled by AT-STE=1, AT-STE=3, AT-STE=5, or AT-STE=7):
This feature does not apply in voice mode.
Extension Pickup
(Enabled by AT-STE=2, AT-STE=3, AT-STE=6, or AT-STE=7)
If the modem is off-hook and an extension goes off-hook, the modem
issues a <DLE>P to the DTE. The application software should then hang
up the line (VLS=0).
Remote Hang-up (Enabled by AT-STE=4, AT-STE=5, AT-STE=6, or AT-STE=7)
If the modem is off-hook and the remote user goes on-hook, the modem
issues a <DLE>P to the DTE. The application software should then hang
up the line (VLS=0).
Examples:
User is talking on an extension and the modem tries to dial
AT-STE=7
ATDT555-1212
LINE-IN-USE.
The line is not in use and the modem tries to dial
AT-STE=7
ATDT555-1212
Modem goes off-hook
CONNECT