[VoIP] Berry 314A trunk test set (correction)

[Jerry Petrizze]

Thanks Steph:  I will keep you posted.
Jerry.

----- Original Message ----- 
From: "Steph Kerman" <stfkerman at jps.net>
To: "Voice Over IP Tandem for Analog Switches" <voip at ckts.info>
Sent: Sunday, November 04, 2007 2:57 PM
Subject: Re: [VoIP] Berry 314A trunk test set (correction)


> Sorry... 0.8V at the input, not 0.4V.
>
> =SK=
>
> Jerry Petrizze wrote:
> > I feel the same way, why the beat note? But if there is two parallel
> > processes going on which you would expect, is it possible that it is
> > generating the same tone on both channels with just a slight time
> > shift enough to create the beat.? Beats me!!!
> Perhaps there are two test points for examining the output of each tone
> of the pair independently.  Otherwise it would be difficult to evaluate
> the tone quality without complex instruments.
>
> Adding two phase shifted tones of the same frequency would not AFAIK
> produce a beat note.  If the tone samples are fetched from EPROM it
> seems unlikely a circuit failure could cause this to happen.
> > It does exist in both MF and DTMF. However some of the keys sound
> > normal, that's why I thought might be in the key pad logic.?
> I think the keypad is probably a single contact type rather than dual
> contact type.  It's probably scanned by the CPU and interpreted in
> firmware without any dedicated logic other than perhaps an input latch
> or buffer.  Are the keys that do not work properly the same for both MF
> and DTMF?
>
> Perhaps the contact resistance of the keys has risen to the point where
> they do not deliver a valid logic level to the input port.  It sounds
> like you have a scope.  I suggest inspecting the keypad terminals to see
> whether solid logic 0 and 1 levels are appearing there and whether there
> are static levels or whether it is scanned in a matrix.  Remember that
> if the input device is TTL, it needs a logic 0 below 0.4V, which is very
> close to ground, not 33% of Vcc as for CMOS.
> > And yes without a road map your kind of lost. I will keep digging.Jerry
> Good luck!  "Write if you get work..."
>
> Steph
> >
> > ----- Original Message -----
> > From: "Steph Kerman" <stfkerman at jps.net>
> > To: "Voice Over IP Tandem for Analog Switches" <voip at ckts.info>
> > Sent: Sunday, November 04, 2007 1:38 PM
> > Subject: Re: [VoIP] Berry 314A trunk test set
> >
> >
> >> Very hard to say what the problem is without seeing a schematic.  Some
> >> time back Paul doped out some superficial aspects of how it generates
> >> tones.  IIRC it uses a digital technique based on parallel output shift
> >> registers with weighted resistor values to perform a D/A function.
> >> Presumably there would have to be 2 such implementations, with analog
> >> summing otherwise the sample values would have to be summed....
probably
> >> beyond what they would attempt with a 6800 family CPU.
> >>
> >> If only one tone is present, how can it be that you hear a beat note?
> >> That seems contradictory.
> >>
> >> Is the problem evident on all keys in both MF and DTMF modes?  Specific
> >> keys only?
> >>
> >> Steph
> >>
> >> Jerry Petrizze wrote:
> >>
> >>> Thank you anyway Paul since I did not have the Ops. manual for it
ether.
> >>>
> >>> Steph: Everything seems to work on it except the tones are messed up.
> >>> Like when you press the # one key in the MF mode you hear a beet note
> >>> and one tone. If you look at the test point where the tones can be
> >>> checked you just see one tone being generated. I believe the problem
> >>> lies in the key pad interpolation circuitry.???
> >>> Jerry P.
> >>>
> >>>
> >>> ----- Original Message -----
> >>> From: "Steph Kerman" <stfkerman at jps.net>
> >>> To: "Voice Over IP Tandem for Analog Switches" <voip at ckts.info>
> >>> Sent: Sunday, November 04, 2007 12:42 PM
> >>> Subject: Re: [VoIP] Berry 314A trunk test set
> >>>
> >>>
> >>>
> >>>> Same experience here.  What is the problem with it?
> >>>>
> >>>> =SK=
> >>>>
> >>>> Paul Wills wrote:
> >>>>
> >>>>
> >>>>> Oops, I guess you meant documentation for maintenance. Good luck. I
> >>>>>
> > was
> >
> >>>>> never able to get anything like that out of Berry.
> >>>>>
> >>>>> PDW
> >>>>>
> >>>>> ----- Original Message -----
> >>>>> From: "Jerry Petrizze" <t2600 at sbcglobal.net>
> >>>>> To: "Voice Over IP Tandem for Analog Switches" <voip at ckts.info>
> >>>>> Sent: Sunday, November 04, 2007 3:36 PM
> >>>>> Subject: [VoIP] Berry 314A trunk test set
> >>>>>
> >>>>>
> >>>>>> Help!!! Needed, service documentation on a Berry 314A Trunk Test
Set.
> >>>>>> Thank you Jerry Petrizze
> >>>>>>
> >>>>>>
> >>>>>>
> >>>> _______________________________________________
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> >>>>
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> >>>
> >>>
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> >
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