I enjoy re-purposing misc items and components to make neat gadgets etc. I have salvaged these two "switches" from an old marine radio. The rods on each click in and click out and rotate in both clicked-in position and clicked-out position. The only writing on them is "503B 33 3F" on one. And "800503B 33 3F" on the other.

I know most people talk about looking up data sheets for things like these, but I am unable to find a data sheet for them. Any description of their function or a link to a data sheet would be greatly appreciated. Thanks!

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    \$\begingroup\$ If they rotate, they most likely contain a potentiometer. And if you can push on the rod to make a click it most likely contains a switch as well. Such combinations are not unusual. Turn the knob halfway and put your multimeter in resistance mode and probe around. Keep in mind that the potentiometer can be either linear or ligarithmic. \$\endgroup\$
    – Oskar Skog
    May 19, 2019 at 7:42
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    \$\begingroup\$ A rotating rod that clicks in and out might also be a pair of potentiometers that you can switch between -- like the balance/fader knob on an old car radio. Or an old boat radio. :) \$\endgroup\$
    – user39382
    May 19, 2019 at 10:02
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    \$\begingroup\$ If they are from newer microprocessor-controlled radios, they may be rotary encoders, rather than potentiometers. Pushing the shaft in will operate a switch. \$\endgroup\$ May 19, 2019 at 16:09

1 Answer 1


So, Oskar Skog, you were spot on! I ended messing around with the multimeter and yes, it changes the resistance with the rotation and the click is a switch to a different set of terminal on the underside. Also, while messing around with it, I discovered the name ALPS Japan on the back. I was able to find the website. I'll post it just in case anyone else else needs to know or is curious. But it is either a 50ohm, or 100ohm potentiometer with a max rated power of .05w Here's the link>AlpsRotaryPotentiometer

  • \$\begingroup\$ 503B usually represents 50k Linear taper. \$\endgroup\$ Feb 21, 2020 at 4:26

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