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AT Commands Reference Manual
Case 2: Modem off-hook, Extension Pick-up
If the modem is connected and another extension goes off-hook, the modem will send a
GSTN Cleardown to the remote modem and then immediately hang-up. Due to the noise
possibly being added to the line when a telephone extension is picked-up, a GSTN
Cleardown may or may not successfully be received by the remote mode. If the GSTN
Cleardown is not received successfully by the remote modem, the remote modem may
attempt a retrain until the retrain fails and the remote modem drops the line. In any case,
the modem will send a NO CARRIER message to the DTE immediately after sending the
GSTN Cleardown. A result code of 25 will be left in the S86 register.
Because the extension is off-hook, the modem cannot flash the hook for the central office
to generate a dial tone. In this case, the user must flash the extension handset to obtain a
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
100722B
Conexant
3-47