Re-installing a TouchTone keypad in an ASR-33

Mon May 18 16:04:33 CDT 2009

On 18 May 2009 at 16:17, Dave McGuire wrote:

>    Oh, how thoroughly bizarre.  Thanks for the explanation.  I'd love 
>    
> to see a SPICE simulation of that.

What's noteworthy is the stability of the thing.  ISTR that DTMF 
signalling relies on a tolerance of something like +/-2%.  A mass-
produced LC oscillator that operates reliably close to tolerances in 
a steel mill or a meat-packing plant is a marvel.

--Chuck