Chapter 4 - V.22bis Commands

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.

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 S86=25. A line reversal can also be simulated by simply pulling out the telephone line during a connection.

+PCW Call Waiting Enable

This command controls the operation of the modem in the presence of call waiting.

Syntax +PCW=<value>

Defined Values

<value> Decimal number corresponding to the selected operation.

0Collect caller ID information if enabled by +VRID. Toggle V.24 circuit 125. (Default)

1Hang-up.

2Ignore call waiting.

Result Codes OK <value> = 0, 1, or 2

ERROR Otherwise

Reporting Selected Value(s)

Command: +PCW?

Response: +PCW: <value>

Example: +PCW: 0 For the default setting.

Reporting Supported Range of Parameter Values

Command: +PCW=?

Response: +PCW: (<value> range)

Example: +PCW: (0,1,2)

+VDR Distinctive Ring

This command causes the modem to enable or disable reporting of the ring cadence information and to control the timing of the RING event code report if ring cadence reporting is enabled.

Syntax +VDR=<enable>, <report>

Defined Values

<enable> Decimal number corresponding to the selected option.

0The modem will not report ring cadence information.

1The modem will report ring cadence information as specified for the <report> subparameter.

<report> Decimal number specifying ring cadence information report when enabled by <enable> subparameter.

0 The modem will produce only DROF and DRON messages. The modem will not produce any RING event codes. The modem will report other call progress event codes as normal.

Other The modem will produce only DROF and DRON messages. Modem will produce a RING event code after <report>/10 seconds after the falling edge of the ring pulse (i.e., after DRON report).

Reporting Current or Selected Values

Command: +VDR?

Response: <enable>,<report>

Example: 0,0 For the default setting.

Reporting Supported Range of Parameter Values

Command: +VDR=?

Response: (<enable> range),(<report>range)

Example: (0,1),(0-6)

Result Codes OK <enable>,<report> = (0,1),(0-6)

ERROR Otherwise, or if not in Voice Mode

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide

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Multi-Tech Systems MT2456SMI22 manual +PCW Call Waiting Enable, Reporting Selected Values, +VDR Distinctive Ring