I'm new to this field, and I found the below circuit online.

My intention is to use it to connect an Arduino to an 8-PIN Yaesu Rotator controller.

My questions are:

  • What are the parts that I've marked with blue rectangles and how would they appear on a breadboard?

  • What does "01" on capacitors that I've marked with yellow rectangles mean?

  • What do the symbols within the red rectangle represent?

  • What's the difference between a 2N2222 and 2N3904 transistor for this?

enter image description here

  • 1
    \$\begingroup\$ ed190 - Hi, You said: "I found this image online". In order to comply with the Stack Exchange rule for referencing, please edit the question & add a link to the webpage which was the original source for that schematic image. || As you are new here, please see the tour & help center for the main site rules, as they differ from typical forums. Thanks. \$\endgroup\$
    – SamGibson
    Oct 1 at 9:51
  • \$\begingroup\$ Thanks for adding that link to the source of the schematic image. Please note it's your responsibility to do that in future too. \$\endgroup\$
    – SamGibson
    Oct 1 at 10:00
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    \$\begingroup\$ The capacitor marking is ".01" and not just "01". That is significant. Why not look at the data sheets for the two transistors and compare them? Then, if something is still concerning you, you could probably raise that as a much more valid question. \$\endgroup\$
    – Andy aka
    Oct 1 at 10:33
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    \$\begingroup\$ If a cap doesn't specify units it is usually microfarads. \$\endgroup\$
    – Mattman944
    Oct 1 at 17:30

1 Answer 1


The symbol in blue rectangle is a symbol for ground. It's not a physical component, it just means, this connects to ground, in any way you need to do it.

The caps marked with yellow as .01 are likely 10nF, but we can't know for sure what was the intention of the person who designed this, if there is no explanation.

The items marked in red are just symbols for pushbuttons of some sort.

Different transistors are for different uses. Some handle more power, some are faster for higher frequencies. For differences between those two transistors please read the data sheet. If you want to know if you can replace the 2N2222 in the circuit with a 2N3904, we cannot know that as we don't know what the circuit needs to do.

  • \$\begingroup\$ I was reading the github where I found the image ( github.com/k3ng/k3ng_rotator_controller/wiki/… ) that the intention is to connect the arduino to a 8 PIN Yaesu Rotator controller \$\endgroup\$
    – ed190
    Oct 1 at 10:02
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    \$\begingroup\$ @ed190, please edit your question to add new info, don't only drop it in comments. Otherwise, readers have to piece together the full question from scattered fragments. You can obviously draw other users' attention to the revised info in comments, though. Thanks. \$\endgroup\$
    – TonyM
    Oct 1 at 14:26

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