Phone in use circuit not working

On Sun, 03 Mar 2013 13:55:47 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

John Larkin wrote:

On Thu, 28 Feb 2013 18:42:53 -0500, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


steve wrote:

I tested and built the following circuit.

http://www.circuitstoday.com/telephone-in-use-indicator

It all worked fine untill I tried to test it by calling into my phone.
(the one test I didnt do before I soldered it all together)

What happens is taht the phone rings for a about 1/2 a ring then stops ringing.
To my surprise when I life the phone up the line is alive eg. Its like the device has answered the phone.

I think that the circuit must be drawing too much power and then telling the phone that it has been answered, because the voltage has gone down.

I have had to replace the Transistors with NTE199, which according to the book are the same. I have also used a rectifier that is a 2 amp 400v SIP 2KBP04M-1.
Im wondering if I used a different rectifier if that would change the results?

I recognize that your not suppse to take power from the phone co. but I would like to get this circuit working. Can anyone tell me why its not working.
thanks.


I think some one gave you some bad transistor numbers..

THe phone system in the US rings at around 100 Volts AC and on hook
is around 50Volts. Off hook may give you around 10 volts and it depends
on how many phones you have at one time off hook.

The 2N3392 can only handle 25Volts and it may work if you can insure
that the unit will switch on in time to load it down. Further more, the
other transistor will be sitting there with this 50v (on hook), leaking
through the collector.

The NTE199 replacement isn't much better, it has a 70V limit at best
and most likely will work find when on hook, but when it rings, you can
expect some leaking to be taking place.

You first need to get HV transistors.

Try getting some 2N5550 transistors, or the 2N5551 which is a little
higher..
Mouser.com has 2N5551 for 0.78 ech and they have over 3k in stock.


Jamie


How about a pair of back-to-back paralleled LEDs in series with the line? Rings
would be bright, off-hook less bright. Might look cool, especially with
different color LEDs.



Not sure how the audio would sound going through diodes.

Jamie
Click to expand...
No problem. One of the diodes would be forward biased by the DC line current, so
would have a dynamic impedance of a couple of ohms and no significant
distortion.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
 
On Sun, 3 Mar 2013 19:07:32 -0000, "Ian Field" <gangprobing.alien@ntlworld.com>
wrote:

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:ISMYs.81579$KR.62297@newsfe27.iad...
John Larkin wrote:

On Thu, 28 Feb 2013 18:42:53 -0500, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


steve wrote:

I tested and built the following circuit.

http://www.circuitstoday.com/telephone-in-use-indicator

It all worked fine untill I tried to test it by calling into my phone.
(the one test I didnt do before I soldered it all together)

What happens is taht the phone rings for a about 1/2 a ring then stops
ringing.
To my surprise when I life the phone up the line is alive eg. Its like
the device has answered the phone.

I think that the circuit must be drawing too much power and then telling
the phone that it has been answered, because the voltage has gone down.
I have had to replace the Transistors with NTE199, which according to
the book are the same. I have also used a rectifier that is a 2 amp 400v
SIP 2KBP04M-1.
Im wondering if I used a different rectifier if that would change the
results?

I recognize that your not suppse to take power from the phone co. but I
would like to get this circuit working. Can anyone tell me why its not
working.
thanks.


I think some one gave you some bad transistor numbers..

THe phone system in the US rings at around 100 Volts AC and on hook is
around 50Volts. Off hook may give you around 10 volts and it depends on
how many phones you have at one time off hook.

The 2N3392 can only handle 25Volts and it may work if you can insure
that the unit will switch on in time to load it down. Further more, the
other transistor will be sitting there with this 50v (on hook), leaking
through the collector.

The NTE199 replacement isn't much better, it has a 70V limit at best and
most likely will work find when on hook, but when it rings, you can
expect some leaking to be taking place.

You first need to get HV transistors.

Try getting some 2N5550 transistors, or the 2N5551 which is a little
higher..
Mouser.com has 2N5551 for 0.78 ech and they have over 3k in stock.


Jamie


How about a pair of back-to-back paralleled LEDs in series with the line?
Rings
would be bright, off-hook less bright. Might look cool, especially with
different color LEDs.



Not sure how the audio would sound going through diodes.


Like about 1 3/4V of crossover distortion on a 48V signal.
Click to expand...
No. The DC line current dominates.




--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
 
"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:inh7j89b3v2e9889e2kgij9dq65o0tnkpd@4ax.com...
On Sun, 3 Mar 2013 19:07:32 -0000, "Ian Field"
gangprobing.alien@ntlworld.com
wrote:



"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in
message
news:ISMYs.81579$KR.62297@newsfe27.iad...
John Larkin wrote:

On Thu, 28 Feb 2013 18:42:53 -0500, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


steve wrote:

I tested and built the following circuit.

http://www.circuitstoday.com/telephone-in-use-indicator

It all worked fine untill I tried to test it by calling into my phone.
(the one test I didnt do before I soldered it all together)

What happens is taht the phone rings for a about 1/2 a ring then stops
ringing.
To my surprise when I life the phone up the line is alive eg. Its like
the device has answered the phone.

I think that the circuit must be drawing too much power and then
telling
the phone that it has been answered, because the voltage has gone
down.
I have had to replace the Transistors with NTE199, which according to
the book are the same. I have also used a rectifier that is a 2 amp
400v
SIP 2KBP04M-1.
Im wondering if I used a different rectifier if that would change the
results?

I recognize that your not suppse to take power from the phone co. but
I
would like to get this circuit working. Can anyone tell me why its not
working.
thanks.


I think some one gave you some bad transistor numbers..

THe phone system in the US rings at around 100 Volts AC and on hook
is
around 50Volts. Off hook may give you around 10 volts and it depends
on
how many phones you have at one time off hook.

The 2N3392 can only handle 25Volts and it may work if you can insure
that the unit will switch on in time to load it down. Further more,
the
other transistor will be sitting there with this 50v (on hook),
leaking
through the collector.

The NTE199 replacement isn't much better, it has a 70V limit at best
and
most likely will work find when on hook, but when it rings, you can
expect some leaking to be taking place.

You first need to get HV transistors.

Try getting some 2N5550 transistors, or the 2N5551 which is a little
higher..
Mouser.com has 2N5551 for 0.78 ech and they have over 3k in stock.


Jamie


How about a pair of back-to-back paralleled LEDs in series with the
line?
Rings
would be bright, off-hook less bright. Might look cool, especially with
different color LEDs.



Not sure how the audio would sound going through diodes.


Like about 1 3/4V of crossover distortion on a 48V signal.

No. The DC line current dominates.
Click to expand...
Oops - forgot about that, I was still in on-hook mode.

I put a hand traced schematic of all the discrete transistor circuitry from
a phone, on ABSE over a month ago.
 
steve says...

In my first post I put up a link to the diagram that I
was using for this circuit. One of the comments under
the diagram said that I should use 3.3k Resistor for R2.
Not the 33k that the diagram indicates. This comment was
WRONG. As soon as I put back the 33k into R2 things
worked find.
Click to expand...
That's great. And does the green LED still light up at all?

In my weak defense I have found that diagrams are wrong
sometimes and I have struggled for days trying to get
something to work that in the end would never work
because the diagram was wrong. I was standing on the
shoulders of the comment of another user and they were
wrong. How they got it to work with the wrong R value I
dont know. Unless it was a deliberate mistake.
Click to expand...
I don't think it was malicious. The logic was simply that
the right resistor to light up the green LED was 3.3k, just
like the resistor for the red LED. But that's not quite
right because the source voltage for the green LED is 48V,
not the 10V source for the red LED.

Anyway, congratulations on getting it to work.
 
I wanted to get back to the group as I was the original poster of this. It has certainly generated some discussion.
Anyway I solved my problem.

In my first post I put up a link to the diagram that I was using for this circuit. One of the comments under the diagram said that I should use 3.3k Resistor for R2. Not the 33k that the diagram indicates. This comment was WRONG. As soon as I put back the 33k into R2 things worked find.

In my weak defense I have found that diagrams are wrong sometimes and I have struggled for days trying to get something to work that in the end would never work because the diagram was wrong. I was standing on the shoulders of the comment of another user and they were wrong. How they got it to work with the wrong R value I dont know. Unless it was a deliberate mistake.
Thanks for all your comments they helped me acheive the goal of the finished project.
 
Yes the green LED does light up, although as you or someone mentioned its a little dimmer. Not as bright as the Red. No big deal.

thanks again.
 
On 3/4/2013 11:29 AM, steve wrote:
Yes the green LED does light up, although as you or someone mentioned its a little dimmer. Not as bright as the Red. No big deal.

thanks again.
Click to expand...
I'm glad it works for you, BUT...

It seems to me the transistors 25 Volt rating is a problem during the
90V ring.

I also thought the impedance is way to low and would cause the phone
company to start checking the line for problems.

Anyone disagree with me?

Mikek
 
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