>>a) What would normally happen is that you have a modem at the other end, which then negotiate a connection speed & then come back & tell you at what speed you've connected. If there's no modem, normally you get back a message saying not connected & the originating modem drops the line.
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>>b) To get the OnComm to fire, you need to set the CommEvent & Rthreshold values.
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>>c) I'm not totally sure of what you're trying to achieve, but if I'm right, I think you need a modem with voice capability & suitable sound driver. I think you need to access the sound driver to determine when there is silence & then send the voice mail via the sound driver.
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>>I could be totally wrong & things could be much easier now, it was several years ago I looked at doing something similar (if I understand you needs correctly) & we decided to use a different method because of the complexity & time factor. I'm pushing my memory to the limit now, so sorry if I'm being sketchy.
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>Well, at least, the robot application calls a phone number if something goes wrong with an application. So, if we can take the phone and we hear no voice we presume it has been sent by the robot application. So, we will verify. So, that's the minimum.
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>Now, assuming the call on the cell cannot be completed, that'll go in the voice mail. So, if we are in a zone where the transmission is not good, we would like to have a call recorded in the voice mail. We don't have to record anything. We just want to get up to the end of the voice mail message so this will record a voice mail empty, as we usually have when someone hangs up the phone without leaving a voice mail. <s>
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>So, by that, at least, we will have a voice mail. So, as soon as we become in the zone where the cell reception is better, the voice mail flag will appear on the cell phone.
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>But, the situation is that the voice mail gets fired but the modem seems to loss connection before the voice mail is finished.

Unfortunately, I've got to leave work now - I've got children to pick up.

One thing that you might try is terminating the phone number with ; before chr(13), that way it will go directly to command mode & on answer at the far end it will not try to connect to another modem & it will not drop the phone line.

Then you could play around with timing how long it takes to answer & send the voice mail before closing the port.

Sorry I couldn't help more.

This site has a lot of info about modems that may be of use
http://www.modemhelp.org/