Line Powered Corded Phone - again - Page 2

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Re: Line Powered Corded Phone - again

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A phone left off hook after a call makes very little noise unless the
exchange sends a warning which some have but I dont think all do.

Even Dial Tone is not loud enough to attract attention.

John G.



Re: Line Powered Corded Phone - again

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In the UK they used to have a 'howler', where if a phone was left off the
hook the operator could sreate a howl and increase it in volume until there
was a response from the subscriber. In Aust now you get a short period of
alteranate loud and soft beats and then the phone is disconnected
automatically, although it can be reconnected by clearing down and then
starting again.



Re: Line Powered Corded Phone - again
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I think you will have to "roll your own".

there have been various "off hook indicator" circuits published over
the years.
here is the first one I found that
http://home.att.net/~theremin1/Circuit_Library/line_in_use.htm

Vaguely remember SC did one in recent years that might be approved too
as a bonus.

here is another that seems to specialise in ready built units - that
are also likely to be approved
http://www.spence-electronics.com.au/pdf/SE-Ring%20Indicatoers.pdf
No prices though.

Since they dare to mention the use of incandescent lamps, the "Green
bulb Gestapo" might put them out of business, so better grab one while
you can  ;)


I have never heard of that feature on any consumer phone.

Another alternative is to possibly have the phone wall mounted, and
get one that the handset wont sit anywhere unless its properly hung up

Re: Line Powered Corded Phone - again
On Wed, 25 Feb 2009 07:09:47 +1000, "David L. Jones"

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You wouldn't want a beeper going off when you are talking or dialling,
so the phone would need to be able to distinguish between a
conversation and an accidental off-hook condition, and it would need
to be able to recognise a dialtone. If the phone were to base its
off-hook detection on line current and an absence of sound, then any
background noise such as the TV could defeat it. Therefore it seems to
me that an audible warning would be difficult to implement. However,
one possible way of implementing such a feature might be to sense
whether or not the handset is being held in a person's hand, but this
may run into isolation problems in the case of a line powered phone.
You would also have the beeper going off if you put the phone down in
the middle of a conversation, although in this case the phone could
automatically go on-hold.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: Line Powered Corded Phone - again

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A beeper with a fairly long quiet space like a houshold fire alarm "flat
battery" beeper might work as it would eventually alert the user.
I was about to build such a thing for a blind person a few years ago but he
died and I dropped the project.
John G.



Re: Line Powered Corded Phone - again
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safest way is to have a button you press that kills it for 10 mins or
so at a time.
Maybe start with a small "chirp" every few seconds to warn that the
time out is approaching,
and decrease the delay between the tones.

PIC based device would be easiest, though could be done with 555's

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