Voice Call Establishment - Originate


Directed Originate (Dial as a specific modem type)
For most call originations, it is known ahead of time what type of call is being attempted, and it is acceptable to disconnect if the remote side of the connection does not cooperate. In this case, the modem can be configured ahead of time with the existing +FCLASS (and +FAA=0) or the #CLS command to be a data, FAX, or voice modem.

For Data and Fax Modes, the modem subsequently either succeeds with the desired type of connection, or eventually hangs up.

For the Voice Mode, the DTE has the option of hanging up if there are indications that the remote station has not answered in voice, thus implementing a directed originate for voice. The following are the three connection type choices:

Voice
The modem dials and reports call progress to the DTE, which reduces to reporting NO DIALTONE, or BUSY.

The modem allows the DTE to program a time period, which if elapsed after any ringback is detected, forces the modem to assume the remote has gone off-hook. A secondary time period (safety valve) can define a maximum elapsed time after dialing for receiving no ringback before the modem assumes that the remote has gone off-hook. This safety valve is devised in case the remote picks up the telephone before any ringback is generated, and no other tones are detected. In this mode, the modem is attempting to make a voice connection only and therefore, while waiting for ringback to disappear, it is also feasible to disconnect upon detection something which is definitely not voice from the remote, such as any answer tone. The modem provides detection of "ringback went away or never came".

FAX
The modem dials and reports call progress to the DTE as in all modes. A FAX Class 1 or Class 2 handshake is pursued according to the current configuration.

Data
The modem dials and reports call progress to the DTE as in all modes. A data handshake is pursued according to the current configuration.

Adaptive Originate (Dial with Voice/FAX/Data Discrimination)
The DTE may wish to originate a call which adapts to the remote answerer. For instance, the user may wish to send a voice message if a human picks up the telephone, but a facsimile if a FAX machine answers. The modem can facilitate this type of adaptive originate by extending what it does for the directed originate modes. After determining that the remote station has picked up the line, the modem goes back to Online Voice Command Mode, thus terminating the "connecting state." Once in this mode, the modem reports what it receives from the answerer via specific result codes to the DTE. The DTE can then have the option of pursuing a data, FAX, or voice connection.

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