W
Watson A.Name - "Watt Sun
Guest
Long ago I wondered why the phones and then modems were made the way
they were, why transformers had the word HIPOT on them, and other
mysterious things. Then I found out about FCC Part 68, and its
requirements. Later, I saw some designs that were seriously
deficient, mainly because they were made cheap to sell cheap. Many
cheap phones don't even have a transformer. As for the DAA using the
solid state relay, they don't get into that in this doc.
I found a document that explains some of the circuits and reasoning
behind them. Unfortunately this document doesn't go into designing a
DAA that minimizes RFI, which so often becomes a real problem around
larger installations. In the circuit shown, I would have made the
relay dual contacts so that both sides of the DAA are disconnected
from the line during on hook. This minimizes the unbalance of the
line. Anyway, now I've learned how to calculate REN, always wondered
how they figured that. All I knew was that with the usual cap and
coil, the impedance was several kohms at the ringing freq. Enjoy.
http://www.web-ee.com/primers/files/AN812_1.pdf
~~So Happy Holidays~~
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
they were, why transformers had the word HIPOT on them, and other
mysterious things. Then I found out about FCC Part 68, and its
requirements. Later, I saw some designs that were seriously
deficient, mainly because they were made cheap to sell cheap. Many
cheap phones don't even have a transformer. As for the DAA using the
solid state relay, they don't get into that in this doc.
I found a document that explains some of the circuits and reasoning
behind them. Unfortunately this document doesn't go into designing a
DAA that minimizes RFI, which so often becomes a real problem around
larger installations. In the circuit shown, I would have made the
relay dual contacts so that both sides of the DAA are disconnected
from the line during on hook. This minimizes the unbalance of the
line. Anyway, now I've learned how to calculate REN, always wondered
how they figured that. All I knew was that with the usual cap and
coil, the impedance was several kohms at the ringing freq. Enjoy.
http://www.web-ee.com/primers/files/AN812_1.pdf
~~So Happy Holidays~~
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@