Touchtone Decoder Display

[Don Peterson]

I know this is almost "off-topic", but my justification is the fact that I use
this piece of equipment to restore Heathkit DTMF circuits.

A while ago, I found a touchtone decoder display that was described to me as
having originated from an article in QSL (I think?).  This is a neat little
box that works with an 8748, MC14515, and a Teltone M-957 decoder.  It displays
sequentially any DTMF tones entered into it.  It has 16 7-segment displays that
are driven by the 8748 using segment and digit driver transistors.  On the 8748
is the nomenclature "bigmac.hex" and a date of 2-27-85.  The system uses a 3.579545
crystal for the clock.  There are 3 push buttons labeled "Clear", "Shift", and
"Match".  I figured out what "Clear" and "Shift" were, but have never really
figured out "Match".  It is all mounted on a single sided PC board that could
have either been made by the owner, or purchased as a kit.

The unit still works, but I would certainly like to have a copy of the article
that it came from.  Also the ROM code would be appreciated.  I'd like to keep
this thing running.

Does anyone know of such an article?  Where can I possible find back issues
of "QSL"?  Does anyone know for certain if "QSL" had an article like this?

Any help is greatly appreciated.

I can reciprocate any help with a copy of a Heathkit manual from my collection
at:

http://www.d8apro.com/Heath2.htm

Thanks and Regards

Don

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