MIKE ROSS wrote in a message to Roy J. Tellason:

 MR> "Roy J. Tellason" bravely wrote to "all" (07
Jan 04  20:16:25)  ---
 MR> on the heady topic of "bag of chips"

 RJT> While sorting out some "stuff" I came across this bag of chips...

 MR> Yummy!

 RJT> It was still stapled shut,  so it was apparently meant for something.
 RJT> I don't know if this was a part of an assortment sold as such,  just
 RJT> an assortment of parts,  or if it was meant for some particular
 RJT> circuit.  I suspect the former as it resembles a number of bags of
 RJT> quarter watt resistors I encountered a while back during another
 RJT> session...

 MR> Awww, not the edible kind of chips... :-(

No,  I got into some of those this afternoon,  but that's another echo...

 RJT> Anyhow much of what's in there is pretty generic stuff.  Two things
 RJT> stand out though.

 RJT> One is a chip resembling an op amp,  but apparently preconfigured as a
 RJT> unity-gain buffer.  I found it easily enough in my databooks, though I
 RJT> don't know why you'd get these and not just use a standard op amp and
 RJT> configure it as a unity gain part.  Maybe some difference in the spec
 RJT> that's not apparent to me,  or something...    (Anybody know?)   I
 RJT> suppose I'll think of something to do with these sooner or later.
 RJT> The other part that jumped out at me as being a little unique was a
 RJT> 565 PLL chip.  I have heard of this one before,  but have *no* idea
 RJT> what you'd do with it.  Any of you guys have any thoughts on the
 RJT> matter?

 MR> I think that PLL was part of a series of chips (IIRC 564, 565, 566)
 MR> which were intended for various frequency ranges and uses.

I don't remember either of those other numbers.  I do remember the 567 tone
decoder,  but that's a whole different animal.

 MR> I think the 566 & its cousins was common in project magazine FM 
 MR> radio SCA projects to decode 76KHz (?) subcarrier transmissions.

I thought it was 38KHz.  Maybe there's more than one?  I can see where it
wouldn't necessarily be used much if there are single-chip solutions to
that these days.  I dunno,  I ran across an SCA circuit fairly recently in
my pile of stuff here,  and the author of that particular bit of stuff said
something about how the hookup was no big deal.  What he didn't mention was
that in a normal FM detector you have a de-emphasis circuit in there
somewhere and that this needs to be hooked in _before_ that point.  I
haven't examined the circuits of recent stuff,  don't know how easy that
would be...

 MR> One was also used in DTMF decoder projects but with today's 
 MR> technology it would be a waste of time building as we now have 
 MR> this function in a single decoder IC.

That would probably be the 567 chip.  I have a board around here somewhere
that has a bunch of those on it,  with slightly differing component values
from one stage to the next,  and I'm pretty sure that's what it was for.

 MR> I remember seeing those decoder projects, they used tons of parts 
 MR> to make the filters using first opamps, later the 565 PLL's, and 
 MR> finally a single IC. The original Bell labs used a really 
 MR> complicated switch to connect coils in various configurations to 
 MR> get the dual touch tones.

Those things were incredibly well-built and robust,  though.  Too bad they
can't seem to build phones like that these days!

 MR> I still have one of those early push button switches. What a 
 MR> nostalgic bit of technology. It seems even quainter than vacuum 
 MR> tubes. The analogy sort of like electronics as imagined by a 
 MR> plumber. Perhaps you have a project kit to build a 565 tone 
 MR> decoder to turn on a lamp using the telephone or something like 
 MR> that? :-)

I dunno,  there were a couple of LEDs in the bag too (standard sized red
ones).  I thought I had a Signetics databook around here someplace,  but it
wasn't with the rest of them,  so if I come across it (or come across data
on the web) maybe I'll figure something out...

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