S151 - Simultaneous Voice Data Control

Type
value

Value range
0-1, Default value: 1

Stored by &Wn
yes

Displayed by &V
no

Note: This command has been replace by -SSE.

This register enables simultaneous voice data (SVD) operation.

Value     Action                                              

0         SVD mode is disabled                                

1         SVD mode is enabled while +FCLASS=0

When SVD is enabled the modem exhibits the following behavior:

1. If the telephone is off hook when the D command is received from the DTE, then the modem will mute the telephone, go off hook, and send the SVD start tone every 6 seconds until answer tone is detected or S7 times out. If the modem detects answer tone, the modem will handshake with the answering modem and attempt to establish a SVD connection.

2 If the telephone is off hook when the A command is received, then the modem will mute the telephone, go off hook, and send answer tone. If the originating modem responds, then the two modems will handshake and establish a SVD connection (if S37 permits a line speed of at least 14400 bits/s).

3. If a SVD connection is in progress and the modem receives the H command, then the modem will hangup, return the OK result code, and return connection of the telephone line to the telephone jack.

4. If a SVD connection is in progress and the modem loses carrier, then the modemwill hangup, return the NO CARRIER result code, and return connection of the telephone line to the telephone jack.

5. If a SVD connection is in progress and the telephone is placed on hook, then the modem will continue with a normal data connection. The modem will close the voice channel.
6. If the modem detects the SVD start tone while monitoring a voice call, then the modem will send a RING result code to the DTE. The value of S1 will be incremented each time a start tone is detected. If the value of S0 is greater than 0, then the modem will answer in SVD modem when the number of start tones equals the value of S0. The value of S1 will be incremented each time a start tone is detected.

7. When the SVD mode is enabled, the modem will monitor the telephone line for the SVD start tone while the telephone is off hook. The modem will respond to the SVD start tone as if the tone were the normal ringing signal.

8. If the SVD mode is enabled, a data-only connection is established, and the telephone goes off hook, then the modem will attempt to open the SVD voice channel (by sending suitable XID frames).

9. If the SVD mode is enabled, a data-only connection is established, the telephone is on hook, and the other end signals that the voice channel is open, then the modem will either send ringing voltage to the telephone every 6 seconds or produce a ringing sound in the modem speaker every 6 seconds (until the telephone goes off hook or the attempt to open the voice channel is abandoned by the other modem).

Note: A SVD connection can be added to a data-only connection only if the line speed is at least 14400 bits/s and V.42 LAPM is in use. SVD connections may be established while the modem is in dumb mode or smart AT command mode.

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