Electrical – 3.5mm to DB9 connector (differences)

adaptercablesconnectordb9rs232

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I have 2 different type of connectors of 3.5mm to DB9 that I use to send RS232 commands from device to a screen. The 3.5mm is attached to the device on the serial port and the DB9 to a serial cable and connected to the screen.

Now, I have 2 different devices (A and B) that can send serial commands. The connector on the left works on device A but does not work on B and the connector on the right (with pink tag) works on device B but no on A.

The 'pink' connector has a serial number, and when I Googled it, it says its a CBF Signal, and when I dig deeper it just says its a rs232 connector.

Can someone explain what are the differences between these 2 different connectors and why it works on a specific device where in the end, they are just 3.5mm to DB9 serial connectors?

Best Answer

You have two cables, one works and another does not. What is similarity and what is the difference?

Similarity:

  • both are black cables, looking like the same;
  • both are having DB9 (male or female - can not see on the picture) at one of their ends. You know that DB9 is standard connector and is used is numerous applications and interfaces, standard and non-standard;
  • both are having 3.5 mm stereo jack at another end. Here's the same story, jacks are standard, used in a lot of applications.

Differences:

  • one cable is having stickers on it, another does not. Maybe they have different purpose and made by different companies for different applications?
  • while connectors on the cable ends are standard, their shapes are slightly different. One has label "IN" on it, another does not;
  • one cable has 3.5 mm jack with 4 contacts (TRRS type), another seem to have 3 contacts (TRS type, as far as I can see on your picture).

So it is logical that adapters are not the same. How they are not the same you can find only using the multimeter as @SolarMike suggested.

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