CPC / Disconnect Clear

[mattKnight]

Hi,

Sometimes I have to install Panasonics (TEA308 and 824) on analogue lines. Often part of the requirement is fax detect...

Sure, with a bit of jiggery pokery, this all works (ish). In order to prevent phantom calls (i.e. caller hangs up before answer and phones will continue to ring until answered) I request that the line provider implement disconnect clear (loop current drop) on the lines (usually duration of 500mS). In order to make this work with the panasonics I have to set the CPC to, typically, 46mS (about 10% of the provider set value) to get reliable disconnect. On other PABXs (IP Office) I get reliable results by using about 150mS less than the provider's value.

Why is this? Have I misunderstood how CPC works? Any clues?

Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[cwc3]

I didn't think you's had cpc at all in bt land...
and its not a current drop over hear its an current
reversal!

 

[mattKnight]

>I didn't think you's had cpc at all in bt land...

Maybe we don't...

> and its not a current drop over hear its an current
reversal!

That might be why it performs differently to how I expect. However there is a marked difference between CPC not set and set and that difference achieves may aim.

So does CPC expect a reversal and,in reality, only detect the "edge" transition (hi->low or low -> hi) and that is why it woks for me?

Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[cwc3]

don't rightly know I've been there, have famly
there but have not installed any equipment on that side of the pond....