Telephone switching

[David M]

Hi,

I'm trying to design a circuit to disconnect a telephone if it has
been left off hook after a call and the exchange is sending a
disconnect signal.

The disconnect signal broadcast by this exchange is

400 or 900 Hz
with a 250ms ON 250ms OFF and repeated

I've looked at the circuit on the following page

http://www.p5taylor.btinternet.co.uk/default.htm

This shows how to detect the ringing signal that is modulated onto the
phone line.

Would I do something similar to detect the ON OFF disconnect pattern.

Any hints are welcome.


David

 

[hamilton]

You may want to Google for "call progress" chips.

David M wrote:

Hi,

I'm trying to design a circuit to disconnect a telephone if it has
been left off hook after a call and the exchange is sending a
disconnect signal.

The disconnect signal broadcast by this exchange is

400 or 900 Hz
with a 250ms ON 250ms OFF and repeated

 

[Tim Wescott]

Ross Herbert wrote:

Can I enquire as to why you would want to do this? A means of opening
the line to the offending phone would be possible but this isn't going
to restore the line so that other calls could be received, so my
question is "what for?"



On Mon, 27 Sep 2004 22:31:54 +1200, David M
news^#NO@SPAM^moorhouse#.net.nz> wrote:

|Hi,
|
|I'm trying to design a circuit to disconnect a telephone if it has
|been left off hook after a call and the exchange is sending a
|disconnect signal.
|
|The disconnect signal broadcast by this exchange is
|
|400 or 900 Hz
|with a 250ms ON 250ms OFF and repeated
|
|I've looked at the circuit on the following page
|
|http://www.p5taylor.btinternet.co.uk/default.htm
|
|This shows how to detect the ringing signal that is modulated onto the
|phone line.
|
|Would I do something similar to detect the ON OFF disconnect pattern.
|
|Any hints are welcome.
|
|
|David

It would if you have more than one extension.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[David M]

On Tue, 28 Sep 2004 03:09:06 GMT, Ross Herbert
<rherber1SPAMEX@bigpond.net.au> wrote:

Can I enquire as to why you would want to do this? A means of opening
the line to the offending phone would be possible but this isn't going
to restore the line so that other calls could be received, so my
question is "what for?"

My grandmother lives on her own about 30 minutes away. She's 90 and

sometimes forgets to hang up the phone after someone has called.
The exchange does not reset the line because her phone is a cordless
and holds its connection to the base open.

However I have figured out that if i disconnect the power to the base
for 5 seconds and then reconnect, it resets the cordless handset.
This also resets the telecom line.

So, my plan is to detect the disconnect signal, cycle the (9v) power
to the base and voila - granny's phone is back in action.

Does anyone have any other suggestions.

On Mon, 27 Sep 2004 22:31:54 +1200, David M
news^#NO@SPAM^moorhouse#.net.nz> wrote:

|Hi,
|
|I'm trying to design a circuit to disconnect a telephone if it has
|been left off hook after a call and the exchange is sending a
|disconnect signal.
|
|The disconnect signal broadcast by this exchange is
|
|400 or 900 Hz
|with a 250ms ON 250ms OFF and repeated
|
|I've looked at the circuit on the following page
|
|http://www.p5taylor.btinternet.co.uk/default.htm
|
|This shows how to detect the ringing signal that is modulated onto the
|phone line.
|
|Would I do something similar to detect the ON OFF disconnect pattern.
|
|Any hints are welcome.
|
|
|David

 

[Rich Grise]

On Tuesday 28 September 2004 05:06 am, David M did deign to grace us with
the following:

On Tue, 28 Sep 2004 03:09:06 GMT, Ross Herbert
rherber1SPAMEX@bigpond.net.au> wrote:


Can I enquire as to why you would want to do this? A means of opening
the line to the offending phone would be possible but this isn't going
to restore the line so that other calls could be received, so my
question is "what for?"

My grandmother lives on her own about 30 minutes away. She's 90 and
sometimes forgets to hang up the phone after someone has called.
The exchange does not reset the line because her phone is a cordless
and holds its connection to the base open.

However I have figured out that if i disconnect the power to the base
for 5 seconds and then reconnect, it resets the cordless handset.
This also resets the telecom line.

So, my plan is to detect the disconnect signal, cycle the (9v) power
to the base and voila - granny's phone is back in action.

Does anyone have any other suggestions.

Yes - Get Granny a corded extension for every room. Maybe 2 for big rooms.


Cheers!
Rich

 

[Rich Grise]

On Tuesday 28 September 2004 05:06 am, David M did deign to grace us with
the following:

So, my plan is to detect the disconnect signal, cycle the (9v) power
to the base and voila - granny's phone is back in action.

Does anyone have any other suggestions.

I suggested, rather brusquely, to get a bunch of corded extensions.
I'm not being mean here - what happens to the handheld when the
battery runs down? What you've proposed practically guarantees that
it will.

Good Luck!
Rich