[VoIP] Berry 314A trunk test set

[Steph Kerman]

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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