Microcontroller w/ Modem

By using the phrase "Hayes protocol" in a Google search I found that there are some reasonable links in the first page 1 to 10 of 290,000 or so.

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******************************************************************** Paul E. Bennett .................... Forth based HIDECS Consultancy ..... Mob: +44 (0)7811-639972 Tel: +44 (0)1235-811095 Going Forth Safely ....EBA. *******************************************************************

At a minimum you would need a UART (Serial controller on MCU) with Rx and Tx plus a EIA-232 Buffer. Something like a MAX232A or any of the hundreds if not thousands of similar ICs. You then need to set the modem to use no flow control or Xon/Xoff flow control and to provide the normal status info such as Carrier Detect over the serial link. If the specific version of '705 you are using does not have a UART, then you can bit-bang for low baud rates.

Regards Anton Erasmus