this post was submitted on 26 Jun 2023
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51
What is this device? (infosec.pub)
submitted 2 years ago* (last edited 2 years ago) by [email protected] to c/[email protected]
19 comments fedilink hide all child comments
 

This was inside the bill of a baseball cap with the word "MARINES" on the front. I tried changing the batteries, but it doesn't seem to be doing anything. Does anyone know what this is?

It has a button on one side. But new batteries didn't reveal it's purpose. I'm thinking it's too corroded now to work. I know that round thing is a simple speaker or buzzer, but I don't know (a) what sound it's intended to make and (b) why it was sewn into the bill of a baseball cap.

Internals, image 1:

Internals, image 2:

External, backside:

Cap pictures:

Edit: added images of the internals.

Edit 2: added a small description of the button, and why I didn't just test it with new batteries (I did, but it doesn't work). So, basically, all I know.

Edit 3: added a picture of the backside of the casing.

Edit 4: Adding pictures of the cap itself.

Thank you, everyone, for all of your input. If I'm ever able to get this thing working, I'll add a video of the device and it's audio.

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[โ€“] [email protected] 20 points 2 years ago (1 children)

Looks like one of those recorded message things you find inside greeting cards - the glob of stuff below the black epoxy blob (the ic), looks like a badly corroded button.

Can try cleaning the button up a bit, or removing it entirely, and bridge the connections beneath it.

[โ€“] [email protected] 7 points 2 years ago

It seems to run on some form of electricity!

[โ€“] [email protected] 9 points 2 years ago (1 children)

I've designed similar devices.

The epoxy blob likely plays factory-set chiptunes out the piezo element.

It's unlikely to play voices, just tones. The ones that record arbitrary audio use specific ICs from China, none of which I see there. Also those work with small but standard speakers, not generally piezo elements.

As a small window into how these are designed, a lot of the engineering goes into reducing power consumption and parts count. The button might for example drop the pin of an MCU low to trigger an interrupt that wakes it from deep sleep. Then it plays a tune stored in eeprom (more common) or internal flash (less common). Usually the chips are one-time-programmable and cost under 0.10$!

[โ€“] [email protected] 1 points 2 years ago

That makes perfect sense. Thank you!!

[โ€“] [email protected] 7 points 2 years ago* (last edited 2 years ago)

There is no microchip which means it can't be a listening/recording device. Seeing as the circuit is very simple, my bets would be on it being some kind of oscillator, as I can't see what else you could build using only two components. An oscillator circuit produces a single unchanging, constant tone. I know that circuits making high pitched tones are used to repel moles (in gardens) and teenagers (in shopping centers). I guess they could be used to repel, like, moths as well?

Edit: didn't notice the blank epoxy blob. Yeah that's a microchip

[โ€“] [email protected] 7 points 2 years ago (3 children)

From the other comments, it could be a novelty hat that speaks or makes a sound effect when the button is pressed. Iโ€™m curious to find out what the original sound would have been!

Quick question: Where does the battery go? Is it the corroded part in the first internals image, or was that the button?

[โ€“] [email protected] 3 points 2 years ago (1 children)

It takes 2 button batteries (LR54) under the two metal straps on both sides of the button (center bubble).

[โ€“] [email protected] 3 points 2 years ago

Ah hah, I see it now

[โ€“] [email protected] 2 points 2 years ago* (last edited 2 years ago)

Batteries go in the two steel rectangular holders. The corroded thing is the button (it's a flexible sheet of metal held in place by plastic) The golden disk is a piezoelectric buzzer (think musical greeting cards, which look just like this does inside)

[โ€“] [email protected] 1 points 2 years ago (1 children)

"Semper fi" maybe?

[โ€“] [email protected] 2 points 2 years ago

Makes sense

[โ€“] [email protected] 5 points 2 years ago (1 children)

If I had to guess it's a speaker of some kind.

[โ€“] [email protected] 2 points 2 years ago (1 children)

Well yes but where would the signal come from?

[โ€“] [email protected] 6 points 2 years ago

Signal comes from the "chip-on-board" under the black epoxy blob. Looks like a circuit for simple sample or electronic tune playback. You press the (now damaged) button, and it plays a tune or sound sample(s) out of the speaker.

[โ€“] [email protected] 4 points 2 years ago (1 children)

Can you post what's on the label of the cap? I think that will help tell us who made the item. I couldn't find anything searching the number on the board with the company name on the plastic.

Since it says Marines, I'm thinking this is some novelty item that might play Sousa's Semper Fidelis.

[โ€“] [email protected] 2 points 2 years ago

There is no label on the cap. The adjustment strap, though, is plastic and says "MADE IN USA".

[โ€“] [email protected] 2 points 2 years ago

Is this one of those mosquito repellent noise makers?

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