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 Hi, Jim.
 The first message of this thread, I posted, included
 the attached input circuit. Only two diodes and two
 resistors. Rather wide input gap, bottom threshold
 isn't too close to the ground level. The ability to
 adjust parameters varying value of resistors and
 type of diodes.
  What could IC add to this?
  I'm not faced to some strict specifications here. It's
 me who writes them. (As the Russian sayings goes:
 Chukchi man is not a reader, Chukchi man is a Writer,
 odnako.)
 Almost anybody on the List writes his own
 specifications to small semi-hobby projects, I think.

  Regarding "Tornado" things, I'm not sure Dale gets
 happy when weapon (even old) is discussed on the
List.

Thank you for your response.
 Mike.

Jim wrote:
> Well, Mike, maybe we can adjust some
> of those operational parameters.
>
> >  1. Wider input gap.
>
> How wide? 0 - 50V
>
> How about using a simple resistive divider in
> conjunction with the input interal resistance
> of the line receiver?
>
> Or - how about a resistive divider in front of
> a CMOS 74C14 Schmitt Trigger hex inverter?
>
> You could set your 'trigger' range AND have static
> protection plus direct interface to 5V logic on
> the output ...
>
> >  2. Higher bottom threshold.
>
> A divider network would give you this ...
>
> >  3. Lower input impedance.
>
> EASY to do - add external R's as req'd to lower
> the Z (the 'impedance') ...
>
> >  4. Ability to work from open collector source.
>
> In any case - you would need a "pull-up" to some
> voltage here ...
>
> >  5. Some flexibility to cope with other requirements.
>
> Like? (I didn't follow previous follow-ups to this
> topic so I might be going over some questions that
> have been asked already.)
>
> Some of the airborne mil gear that I have worked on
> in the past used actual "voltage comparators" as
> the active interface device between the outside
> world (where transients and RF can abound) and
> the internal world of "protected" 5V TTL logic
> around the bit-slice processor.
>
> This was on the Panavia Tornado Nose-mounted RADAR
> aboard the tri-country produced all-weather
> bomb-delivery aircraft known as the Panavia
> "Tornado" bomber designed originally for use
> in the European theater as an "all weather
> bomber RADAR-guided weapons delivery platform"
> for use against the perceived 'Red Threat' (or
> 'Red Menace ' <grin>) in previous decades ...
>
> Switch inputs from the cockpit to the LRU 1 (Line
> Replaceable Unit #1), the 'processor/computer'
> were 'buffered' via these circuits using voltage
> comparators (like the uA711, bascially op-amps
> but with no particular emphasis on linearity and
> logic-driving outputs) and protective capacitor
> and resistor networks ...
>
> RF Jim
>
>
> > Thank you, Jim.
> >
> > I'll keep them in my mind. But from the first glance:
> >  I need:
> >  1. Wider input gap.
> >  2. Higher bottom threshold.
> >  3. Lower input impedance.
> >  4. Ability to work from open collector source.
> >  5. Some flexibility to cope with other requirements.
> >
> >  Mike.
> >
> > Jim wrote:
> > > Mike, have you considered simply using something
> > > from the MC1489, MC14C89, SN75189, SN75C189,
> > > DS1489, and DS14C89 family RS232 line receiver
> > > family?
> > >
> > > This chip series is basically billed as a:
> > >
> > >   "ESD-Protected, Quad, Low-Power RS-232
> > >    Line Receiver"
> > >
> > > but will work to 'detect' TTL  and CMOS logic
> > > levels *and* is protected for electro-static
> > > discharge ...
> > >
> > > Brief specs:
> > >
> > >  Input low:     approx. 1 V
> > >  Input high:    approx. 2 V
> > >  Working range: +- 25V
> > >  Approx Rin:    5 KOhms
> >

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