what will be the polarity of the pin and the tube in a barrel connector?

[micky]

I have a new-to-me device, a speakerphone from Radio Shack**, a Duophone
120,that didn't come with a power supply, and it works without one but
is not very loud (and that was the reason I wanted a speakerphone).

It uses 9v dc.

I have two universal adapters (of different amperages). Both have a
polarity switch with 2 sketches of a mini phone plug on them, one with
the tip positive and one negative. But the device needs a tubular
plug, a barrel connector (which both adapters have). If the switch is
set to make the tip negative and the ring positive, what will be the
polarity of the pin and the tube in the tubular plug.

What are the odds I'll burn it out if I connect it backwards?

**BTW, no one seems to sell new speakerphones anymore, unless they are
part of a whole telephone. And even on ebay I didn't find one iirc. At
a hamfest last week I found one for a dollar. When I got home, I found
my own, that I had hunted for. It wasn't in the box of phone
accessories. it was right on top of a stack of something right as I
enter the spare bedroom. I walked by it at least once a month. LOL But
the new one is a lot brighter. The colors of the old one are darker,
probably from sunlight. Not that I care.

My current phone has a base and 3 cordless extensions and it does
everything, but when I don't use the speakerphone, I can't hear the
other party well, and when I do use it, the other party can't hear me
well. To fix the latter problem, I red the manual and saw where the
microphone was and I intended to clean the dirt out of the little hole
in the case next to the microphone. But there was no hole. So I
thought I'd drill one, but I want to know for sure where the mike is,
and I don't want to drill through the case into the circuit. So I took
all the screws out of the case, and it still won't come apart!! I
looked under labels for more screws, but no. Why is there no hole? The
Radio Shack speakerphones have 3 big slits for the mike!

To fix the foremer problem, I cleaned all the dirt out of the holes in
the ear-part of the handset. they filled up agains quickly but even when
empty, I can't hear some people, the soft talkerx. .

[Bob F]

Post by micky
I have a new-to-me device, a speakerphone from Radio Shack**, a Duophone
120,that didn't come with a power supply, and it works without one but
is not very loud (and that was the reason I wanted a speakerphone).
It uses 9v dc.
I have two universal adapters (of different amperages). Both have a
polarity switch with 2 sketches of a mini phone plug on them, one with
the tip positive and one negative. But the device needs a tubular
plug, a barrel connector (which both adapters have). If the switch is
set to make the tip negative and the ring positive, what will be the
polarity of the pin and the tube in the tubular plug.

The power supply amp rating should be as high as the phone requirement.
should be.

In not too old of devices, there is usually a polarity symbol somewhere
on the phone.

Try measuring the voltage at the connector on the phone. the polarity of
the supply plug should match the polarity at the phone. If you see no
voltage at the phone jack, it could be because it has a protective
diode, which lessens the chance that the wrong polarity would fry
things. You could open up the phone and try tracing the wires from the
jack to a nearby capacitor, then check whether that wire is connected to
the positive or negative terminal of the cap.

Post by micky
What are the odds I'll burn it out if I connect it backwards?

Significant.

Post by micky
**BTW, no one seems to sell new speakerphones anymore, unless they are
part of a whole telephone. And even on ebay I didn't find one iirc. At
a hamfest last week I found one for a dollar. When I got home, I found
my own, that I had hunted for. It wasn't in the box of phone
accessories. it was right on top of a stack of something right as I
enter the spare bedroom. I walked by it at least once a month. LOL But
the new one is a lot brighter. The colors of the old one are darker,
probably from sunlight. Not that I care.
My current phone has a base and 3 cordless extensions and it does
everything, but when I don't use the speakerphone, I can't hear the
other party well, and when I do use it, the other party can't hear me
well. To fix the latter problem, I red the manual and saw where the
microphone was and I intended to clean the dirt out of the little hole
in the case next to the microphone. But there was no hole. So I
thought I'd drill one, but I want to know for sure where the mike is,
and I don't want to drill through the case into the circuit. So I took
all the screws out of the case, and it still won't come apart!! I
looked under labels for more screws, but no. Why is there no hole? The
Radio Shack speakerphones have 3 big slits for the mike!
To fix the foremer problem, I cleaned all the dirt out of the holes in
the ear-part of the handset. they filled up agains quickly but even when
empty, I can't hear some people, the soft talkerx. .

[Jamaal Bowman]

Post by micky
I have a new-to-me device, a speakerphone from Radio Shack**, a Duophone
120,that didn't come with a power supply, and it works without one but
is not very loud (and that was the reason I wanted a speakerphone).
It uses 9v dc.
I have two universal adapters (of different amperages). Both have a
polarity switch with 2 sketches of a mini phone plug on them, one with
the tip positive and one negative. But the device needs a tubular
plug, a barrel connector (which both adapters have). If the switch is
set to make the tip negative and the ring positive, what will be the
polarity of the pin and the tube in the tubular plug.
What are the odds I'll burn it out if I connect it backwards?
**BTW, no one seems to sell new speakerphones anymore, unless they are
part of a whole telephone. And even on ebay I didn't find one iirc. At
a hamfest last week I found one for a dollar. When I got home, I found
my own, that I had hunted for. It wasn't in the box of phone
accessories. it was right on top of a stack of something right as I
enter the spare bedroom. I walked by it at least once a month. LOL But
the new one is a lot brighter. The colors of the old one are darker,
probably from sunlight. Not that I care.
My current phone has a base and 3 cordless extensions and it does
everything, but when I don't use the speakerphone, I can't hear the
other party well, and when I do use it, the other party can't hear me
well. To fix the latter problem, I red the manual and saw where the
microphone was and I intended to clean the dirt out of the little hole
in the case next to the microphone. But there was no hole. So I
thought I'd drill one, but I want to know for sure where the mike is,
and I don't want to drill through the case into the circuit. So I took
all the screws out of the case, and it still won't come apart!! I
looked under labels for more screws, but no. Why is there no hole? The
Radio Shack speakerphones have 3 big slits for the mike!
To fix the foremer problem, I cleaned all the dirt out of the holes in
the ear-part of the handset. they filled up agains quickly but even when
empty, I can't hear some people, the soft talkerx. .

Maybe try one of these

https://www.amazon.com/Hamilton-CapTel-Captioned-Touch-Screen-Amplification/dp/B00ZYHA1KI/