Analog modem emulator?

[Tony Duell]

> 
> On 8/2/05, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
> > >
> > >...essentially simulates a telephone
> > > network.... sold by Black Box.
> > 
> > I am surprised, but I have never seen a published schematic for such a
> > unit, neither in a magaxine or on the web. They can't be _that_
> > complicated, surely?
> 
> Having a) looked at competitors features, and b) built similar
> products myself, the ones for sale are not simple.  Ours used a pair
> of SLICs (Subscriber Line ICs) just as a proper PBX or Telco switch

You and I have different ideas of 'simple'. A copuple of SLICs and a 
microcontroller is not complicated, at least not compared to many other 
projects that I've built, and that I've seen in the magazines, over the 
years.

One UK magazine published a design for a telephone exchange. It handled 
16 lines, expandable to 32. It was a load of CMOS logic, crosspoint 
switch ICs, analogue stuff, etc. No microcontrollers (I think there was 
an EPROM to handle the mapping from the telephone number to the 
switches), no special SLICs It alloweed several simultaneous connections, 
produced dial tone, engagued tone, etc

Surely a 2 line box that produces the right tones and the ringing voltage 
would be a lot simpler than that.

-tony