Manual and Dial Phone Gate/Trigger

By collecting some infos here and there on the forum (thx @fredrik), i make this little schem for a Manual & Dial Phone Gate/Trigger, and I ask you if that seems correct to you
maybe add a 10uF cap on the 12V to GND
thank you in advance


With 10K pot and 14K resistor, it’s more like 0->5V, not 0->7V.

Why not use the switch of the IN jack to select the source of the voltage (jack or pot) ?
Or better use this (this is a classic…) :
If nothing is plugged in the jack, T and TN are connected and you can select the voltage with the pot.
If you plug something in the jack, T and TN are disconnected, and the pot is used as an attenuator for the incoming voltage.
That’s two for one, and you save a switch…

I don’t think the 1K on the output is useful in this case, there isn’t much it can protect from overcurrent… but I let more competent people give a definitive answer, there is a pot after all… :slight_smile:


thx @eric, and yes of course for the jack trick ! but i have yet only standard jack socket and some switch, I would surely change when I had cut-off jacks :wink:

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When your pushbutton is open and no one’s dialing, the output is floating. Add a pulldown resistor to ground.


ok thank you @analogoutput

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plz If i add this inverting opamp circuit, can i have some inverting pulse out ?

like this :



This seems fine by me!


Do you want a negative pulse (-5V when switch pushed else 0V) or an inverted positive pulse (0V when switched pushed else 5V)? This will do the former.

(5k, not 7k, because as @eric said, with R=14k you don’t get 7V. For 7V you need 12x10k/(R+10k) = 7 => R = 7k, call it 6.8k for a commonly available value.)


I rather imagined an inverting Gate/Trigger pulse signal, so i think it’s an “inverted positive pulse (0V when switched pushed else 5V)”

for the ~7V i take it in this topic

if this circuit give me 5V and not 7V i think it’s still ok for Trigger/Gate signal .

I think if i use an opamp for an invert out, and i take a TL072, i can maybe add a second output like this

or not ? :grinning:



That means remove 7V from the 12V, so there are only 5V left.


:upside_down_face: ah ok (i made a bad traduction) thanks !

Does the schematic for an additional output look good to you ?

The “inverted” output will not be 0V with pushbutton closed, +5V with pushbutton open. If that’s what you want I think you could do something like this

(Not that sure about resistor values though)

[Edit: But that will only give you 0V or 5V regardless of pot setting. I guess you could connect the top to the pot wiper instead of +5V? But then if you have a CV plugged in I’m not sure if that would be advisable. Maybe OK, maybe would be better with a CV buffer. I think you also could do the inverted output with an op amp, inverting amp plus an offset:

I think that works.]

As for two outputs I’d buffer both.


thanks for all this informations


so where exactly are you connecting the rotary dial too, I like it so far and have a couple different dials and just curious to what points on your dial did you hook it up, thanks probably over simpilfied and over looked by me .

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The Dialphone have only 4 wires inside, “in” and “out” (or “out” and “in” because it works on the both side) 2 x the same thing, take a multimeter or a pilote light to find the good 2 wires.

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Mine was similar. It has the in/out (the two wires that are interrupted when the dial is dialing). Those two wires are where the mechanical magic happens. The second set of wires mine has are interrupted until the dial is rotated and then they stay connected until the dial returns to the resting position. That’s what I wired my little LED circuit into.

You can see the darker pair of wires are for the interrupt circuit. I also was able to attach mine using the screws on the side much like the way the glass covers for ceiling lights are attached.


Also, I’m definitely following this thread to borrow the brilliant ideas coming out of it.


thanks and yes now I see on my victim ( phone) the wiring , and away we go to the project, stay safe and healthy


I already posted it in “My build progress”, but I add it in this thread.

A simple trick to block the Dial

when the dial stopped, I didn’t want the circuit closed continuously.
A small hole and a screw and voila, now I have a choice (allways open/allways closed when you don’t use the Dial)

A short test with a pilot light

I use this style of screw (guitar pedal one)


Yes i’ve seen yours ! nice :slight_smile:

Here’s the begining of the panel

And to attach mine i made 2 small piece of aluminium