In a message dated 10/9/2002, Jeffrey Race writes:
> I am trying to avoid using telset IC for very simple requirement > where I don't need dtmf and ringer functions. > > Could be either carbon, dynamic or electric mic in handset. > Hi Jeffrey: I don't know where such a design might be posted or published, but if you are not able to find a suitable design, I might be able to sketch something out for you. In thinking about this, a few questions come to mind: 1) Will your application require isolation from the phone line? 2) Do you intend to power it from the phone line? 3) Does the resulting design have to comply with the regulatory requirements for connecting to the public telephone network? 4) You say that the mic in the handset "could be either carbon, dynamic or electric mic." Do you mean that the circuit must operate with any of these, or that you are free to specify any one of these for your application? The interface circuits for these three types of handset tend to be incompatible. Some of the telephone chips that you are trying to avoid are fairly low in cost, so it may turn out that a phone IC is still a reasonable solution, even though you don't use some of the functionality. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com
