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On Feb 26, 6:06 am, Franc Zabkar <fzab...@iinternode.on.net> wrote:
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
safest way is to have a button you press that kills it for 10 mins orOn Wed, 25 Feb 2009 07:09:47 +1000, "David L. Jones"
altz...@gmail.com> put finger to keyboard and composed:
In addition to the thread not so long ago on line powered corded phones, now
I happen to be after one.
Plenty available of course, but I've been asked to source one that
specifically has an off-hook audible warning beeper.
All the phones I've looked at online don't have it listed in the specs, so
if they do have it it's buried away in the manual which is next to
impossible to find online.
Any leads?
Thanks
Dave.
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.
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