ZyXEL Communications COMET 336 User Manual page 65

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volume by a value of 5 units. The <DLE>d code can be used to adjust the volume within

the range of 128-228. (See <DLE><u> and <DLE><d> in Section 7.3.2.)

Cancel. Sent during Voice Transmit Mode to indicate that the DTE has finished

transmitting a voice message and wants the modem to discard any remaining data in the

voice transmit buffer. The modem immediately purges its buffer, and then responds with

the VCON message entering Online Voice Command Mode. (This command is ignored

by the modem when not in Voice Transmit Mode.)

Voice Bytes Buffered Query. Sent during the transmission or reception of voice/audio

data, by embedding the command in the voice data stream, to learn the number of

corresponding bytes buffered by the DCE at the moment the <DLE><EOT> command is

received by the DCE. <DLE>XZBBC=n<DLE> is returned by the DCE, in which "n"

represents the number of bytes buffered as a two byte hexadecimal value.

Terminate. Sent during Voice Transmit Mode to indicate that the DTE has finished

transmitting a voice message. The modem completes transmission of any remaining data

in the voice transmit buffer before responding with the VCON message and entering

Online Voice Command Mode. (This command is ignored by the modem when not in

Voice Transmit Mode.)

7.2.6 Voice Record

To effect recording of a message received via a handset or microphone, the DTE must

configure the modem for Voice Mode (#CLS=8), and select the proper relay setup

(#VLS) to instruct the modem whether to use the auxiliary device. The modem responds

to the #VLS command by issuing a relay activate command to select the input device.

When a device other than the telephone line is selected, the modem immediately enters

Online Voice Command Mode (indicated by VCON). DTMF detection is therefore

enabled as soon as the DTE selects the device, such as a handset, although the user still

needs to physically pick up the telephone and press buttons. Even if the DTE has not

entered Voice Receive or Transmit Modes (#VTX or #VRX), these DTMF tones are

delivered via shielded codes identically to when a physical telephone connection exists

but the DTE has not yet commanded receive or transmit. When the DTE decides to

record the message, it issues the #VRX command and upon command receipt, the

modem immediately switches to Voice Receive Mode. Since the microphone or handset

is switched in, the modem immediately issues the CONNECT message indicating that

the modem has switched to Voice Receive Mode and is beginning the transfer of

ADPCM voice or PCM audio data as well as shielded DTMF tones, and other tones

and statuses.

In this recording state, the modem (if so configured) monitors for line silence. If the

#VSP period expires, the modem sends the <DLE>q or <DLE>s code to the DTE.

58 Voice Operation

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