Line Powered Corded Phone - again

[KR]

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

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

 

[Alan Rutlidge]

Hi Dave,

I'm in Dallas Texas. I have a Panasonic corded desk phone.
Yes, the telco switch will kill the circuit after some time.

I suppose I should tell you that I have exceptional high frequency
hearing. Though I haven't been tested recently, at age 28, I was
hearing far higher than average. Seems my ear drums are both
larger than average and tight. The down shot is that loud is painful
to me.

I probably should go get tested again to see how time has altered
my range.

The voice frequencies on a telephone line only extend to 3.4kHz, so I doubt
you have exceptional high hearing based on your statement and observations.

 

[Jasen Betts]

I just plugged in an old Optus phone I found, and I could barely hear it
half a meter away in a very quiet room.
Also, the off-hook signal only goes for about a minute and then switches off
to just an even quieter static. Do others get the same thing?

If you leave it off long enough (hours?) the exchange (on request of a
third party?) will 'buzz' you.

this is a much louder noise than the dialtone you get upon first
lifting the handset.

 

[Lord Garth]

Why would the off hook signal from the telco not be sufficient noise?

The voice frequencies on a telephone line only extend to 3.4kHz, so I
doubt you have exceptional high hearing based on your statement and
observations.

In the context I stated that I had been tested. Testing was at a hearing
clinic and
I do have exceptional high frequency hearing. I never stated that a phone
was
used to test my hearing. What you are probably missing is that a hearing
test
consists of both frequency and amplitude tests. These are randomly mixed.
During the test, the subject can't see the test giver. You only raise your
hand
when you hear a tone in the headphones. They test left & right ears
together and
individually at various frequencies and amplitudes. The whole procedure was
about a half hour in length.

As a general rule of thumb, the ability to hear high frequencies goes
together with
low volume since the ability is based upon the area of the tympanic membrane
and
how taut is that membrane. Usually a large area implies a loose membrane
but not
always.

 

[Lord Garth]

I had my hearing tested once too as part of a job appointment.
They stuck me in a booth with headphones and a push-button to press when I
heard the tone. No tone came so I never pushed the button. They ran back
in screaming and doing hand signs saying I must be legally deaf! My first
response of course was to jokingly scream "WHAT?? with my hand to my ear!
You guessed it, the button was faulty.
Once fixed I eventually got well above average too.

It's almost certain that your being able to hear the phone in the next
room has more to do with the phone system were you live than your low
volume hearing ability (as having exceptional hearing you must have the
volume turned down too of course?)
It looks to be not possible here in Sydney with a conventional phone at
full volume. And of course it cuts off after a minute anyway.

Dave.

I'll bet that was funny!!!! The headphones I was given where rather old but
they did work.

I'd agree that the telco has everything to do with me hearing the warble.
The
odd thing is that the cat kicked the receiver off hook only last weekend.
Lately
he has taken to walking on the phone as I'm having a conversation. I
suppose
he simply wants attention.

I'm glad there is no quick dial button for 911 service!

BTW, Ninja is a tomcat I rescued from my crappy neighbors. He's fixed but
he does have his nails. He'll sharpen them on a tree then run up to hunt
for birds.
I haven't had a pet in 30 years and never were any past pets cats.

 

[David L. Jones]

In the context I stated that I had been tested. Testing was at a hearing
clinic and
I do have exceptional high frequency hearing. I never stated that a phone
was
used to test my hearing. What you are probably missing is that a hearing
test
consists of both frequency and amplitude tests. These are randomly mixed.
During the test, the subject can't see the test giver. You only raise
your hand
when you hear a tone in the headphones. They test left & right ears
together and
individually at various frequencies and amplitudes. The whole procedure
was
about a half hour in length.

As a general rule of thumb, the ability to hear high frequencies goes
together with
low volume since the ability is based upon the area of the tympanic
membrane and
how taut is that membrane. Usually a large area implies a loose membrane
but not
always.

I had my hearing tested once too as part of a job appointment.
They stuck me in a booth with headphones and a push-button to press when I
heard the tone. No tone came so I never pushed the button. They ran back in
screaming and doing hand signs saying I must be legally deaf! My first
response of course was to jokingly scream "WHAT?? with my hand to my ear!
You guessed it, the button was faulty.
Once fixed I eventually got well above average too.

It's almost certain that your being able to hear the phone in the next room
has more to do with the phone system were you live than your low volume
hearing ability (as having exceptional hearing you must have the volume
turned down too of course?)
It looks to be not possible here in Sydney with a conventional phone at full
volume. And of course it cuts off after a minute anyway.

Dave.