Intel MD566X manual Dtmf Detection, Relay Control

56K V.92 Data, Fax, and Voice Chipset

6.1 DTMF Detection

DTMF detection information is handled differently than other detection information. IS-101 specifies that more than one <DLE><DTMF CHAR> character pair may be sent for a single DTMF tone burst. As such, the modem sends delimiter <DLE> character pairs to indicate the end of a tone burst. When a DTMF tone is detected in playback or command mode, the modem sends <DLE><DEL> to indicate the end of a burst. For example, from a single burst of DTMF 5 tones, the following reports are possible:

Playback and voice command modes:

<DLE><5><DLE><DEL>

When a DTMF tone is detected in the record mode, the modem sends <DLE></> to indicate the beginning of a tone burst. The modem may then send one or more <DLE><DTMF CHAR> character pairs followed by <DLE><DEL>, which signifies the end of the tone. For example, from a single burst of DTMF 5 tones, the following reports are possible:

Record mode only:

[voice data]<DLE></><DLE><5>[voice data]<DLE><DEL>[voice data]

[voice data]<DLE></><DLE><5>[voice data]<DLE><5>[voice da- ta]<DLE><DEL>[voice data]

6.2 Relay Control

To originate a call (that is, to originate call forwarding or auto-dialing) and to generate tones, use the dialing command:

ATDT <telephone number>

If the modem was not already off-hook, then this command automatically configures the value for AT+VLS=n to n=1 or n=5 depending on the value for Mn.

To answer a call, use the AT+VLS=n command. Unlike data mode, the modem (when configured for voice mode) does not automatically answer an incoming call (that is, the modem ignores the contents of S-register S0).

Remote playback/record takes place whenever the modem is off-hook (OHREL* is activated). For local playback/record, the modem is on-hook, and the user uses a local telephone or handset. The LPHREL* relay driver may be used to control the local telephone or handset when implementing local playback/record mode (AT+VLS=n). Additionally, voice messages may be played through the modem/computer speaker. The FastPath chipsets also provide a microphone interface that can be used for local recording.

In voice mode, all voice AT commands can be issued by the DTE at any valid speed between 300 bps to 115,200 bps. Typically, the DTE-to-modem data rate is set for 19,200 bps, which is the recommended data rate for Class 1 fax mode. The DTE-to-modem data rate may need to be set to 115,200 bps in certain instances, such as during playback or during record mode for a CL1 compression scheme.

The following data and fax AT commands are supported in voice mode:

Data: All except ATA, ATIn

Fax: +FCLASS

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