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What can an oscilloscope be used for with phones?

Started by bdoss2006, November 20, 2022, 02:36:08 AM

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bdoss2006

I was curious if they could be useful in any way.

FABphones

The Search option (above) entering the word 'oscilloscope' will give you a minimum (as of this post) 35 results. That should start you off nicely on a read up.

:)
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bdoss2006

Quote from: FABphones on November 20, 2022, 04:30:38 AMThe Search option (above) entering the word 'oscilloscope' will give you a minimum (as of this post) 35 results. That should start you off nicely on a read up.

:)
well looks like they can be used to check the speed of a dial. How exactly do you do that? I thought they might could be useful with checking fingers maybe.

ka1axy

Quote from: bdoss2006 on November 20, 2022, 11:46:53 AMwell looks like they can be used to check the speed of a dial. How exactly do you do that? I thought they might could be useful with checking fingers maybe.
I checked a dial (installed in a 500 set) yesterday. It's quite easy. You need a scope with digital storage (e.g.: Rigol, Siglent or similar) and cursors,  and a power supply with foldback current limiting (I have an HP 20V/1.8A one). I set the current limit to 10mA and the voltage to 12V. Attach the power supply leads to the tip and ring leads of the phone. When you go off hook, you should see 10mA of current on the supply. Hang up and you should see 0 mA. The power supply voltage will drop to whatever it needs to when the phone draws 10mA.

Attach the scope to the same terminals - ground clip to negative and probe tip to positive. Go off hook and you should see the voltage drop. Dial and the scope trace should show pulses. Adjust and measure as needed.

SUnset2

#4
I use a BK 1045A as a source of battery feed, and a digital storage scope to test dial speed.  You could use a PBX, or any other source of dial tone if you don't have a BK 1045A or such.  Before you hook the scope probe across tip and ring, be sure to check to see which terminal is at ground potential before hooking up the ground lead, otherwise you might damage your equipment.  A cheap alternative source could be a battery and a current limiting resistor.

I should add that it would be difficult to measure dial speed with a standard analog oscilloscope.  The dial pulses don't continue long enough to get a measurement on them.  A storage scope is optimal.  An analog storage scope would work, but digital storage scopes are more common these days.

G-Man

Quote from: bdoss2006 on November 20, 2022, 11:46:53 AMwell looks like they can be used to check the speed of a dial. How exactly do you do that? I thought they might could be useful with checking fingers maybe.
Dated Info but still shows the concept...

G-Man

Wasting bandwidth :-\ ...

I just noticed that my response was to a very dated thread, so it's no longer relevant!

ka1axy

New information is always relevant...maybe not to the original poster, but that doesn't matter :-)