Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!snorkelwacker!bloom-beacon!eru!hagbard!sunic!mcsun!ukc!stc!rajesh
From: rajesh@tcom.stc.co.uk (Rajesh Kirpalani)
Newsgroups: comp.dcom.modems
Subject: Invisible modems ?
Keywords: Modem RS232 UNIX Sun
Message-ID: <1909@jura.tcom.stc.co.uk>
Date: 29 Aug 90 11:50:42 GMT
Organization: STC TSD-E, Access Systems Engineering, Harlow. ESSEX
Lines: 48





   
       I am working with a Sun 386i running SUNOS 4.0.1 with an Amstrad
       SM2400 modem. 
       Conventialy an RS232 cable can be used to connect a computer and 
       a device. A suitable application could send/receive data from the
       device.
  
            | SUN | ==== RS232 ===== | Device |

      Suppose if we wanted to connect a device to a computer over longer
      distances a solution might be to use modems.

 Calling DTE                                               Answering DTE

 | SUN | === RS232 ===| Modem | _ _ _ Tel _ _ | Modem | ==== | Device |

      The Sun will always calls the device. The modem at the device end is
      given  the  command : ATS0=1 (Answer  the  phone in one RING). 
      (I configured the modem by connecting a dumb terminal and then
      connecting it to the 'device' once configured.)

      On the Sun I am using the command :-

           ( stty 2400 ; echo ATD number ) > /dev/ttya

       The above does not work. The modem does not execute the Hayes command. 
    I have successfully used the UNIX program tip and entered Hayes commands.
    The reason I cannot  use tip is that it interfers  with the application 
    that is going to be using this 'device'.
    (Application reports problems about two processes cannot share one port (?))
    
      So the solution must dial the the 'device' and remain invisible to the
    application. Can anyone  tell me  why the  modem is not responding  even 
    though a when a dumb terminal installed instead of the modem  at the SUN;
    the command was successfully echoed on the terminal screen.

    
    Does any one know what the problem is ? Any solutions/ideas/pointers 
    would be most welcome.


********************************************************************************STC Harlow
Rajesh Kirpalani                                   rajesh@jura.tcom.stc.co.uk
*******************************************************************************