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Phone in use circuit not working

J

Jamie

Jan 1, 1970
0
Michael said:
Or surely a modem, just uinsg the "DAA" part. Even the "winmodems".
THere has to be an off-hook indicator to tell the modem the line's not
available.

I recall back when this sort of circuit seemed to come up here over a
decade ago, John whatshisname suggested something so that when his modem
went online, it disconnected the other phones in the house. Obviously
he had to arrange things right he could control the rest of the phone
wiring in the house.

Michael
which is why they made modems with a line in and phone out...

Jamie
 
J

Jamie

Jan 1, 1970
0
Jasen said:
some modems had a switched socket that would be disconnected from
the line when the modem went off-hook, some had the pads but just
had wire links in place of the relay.

A second relay was needed as the main relay was also used for pulse
dialing.
Seems like in my distance past I used a low voltage low current Reed
relay in series with the phone line with a by pass zener pair to
protect it from higher voltages.

Jamie
 
J

Jon Kirwan

Jan 1, 1970
0
Seems rather elaborate when 1 resistor, 1 capacitor, 1 diac & 1 LED would do
the same job just as well.

It's a reliable design, as I've built a couple, at least.

I've not used diacs, yet. Just a hobbyist. But yes, I can see
how that should work. Breakover voltage is higher, which has
its advantages in this application.

Any particular diac you'd consider trying?

Jon
 
J

Jamie

Jan 1, 1970
0
John said:
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
 
S

steve

Jan 1, 1970
0
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.
 
P

Peabody

Jan 1, 1970
0
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.

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.

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.
 
S

steve

Jan 1, 1970
0
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.
 
A

amdx

Jan 1, 1970
0
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.

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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