The four pins
Four pins, three of them wired: GND on the square pad, VCC for the buzzer, and SIGNAL into a transistor through 1 kΩ. NC is connected to nothing. HIGH on SIGNAL beeps and LOW stops it, which is what ACTIVE HIGH on the front and BEEPS WHEN GPIO IS HIGH on the back both say.
Three wires and a spare
The header is four right-angle pins, 2.54 mm apart, printed GND, VCC, NC and SIGNAL from left to right with the parts facing you. GND is on the square pad, and that pad is the only way to tell four identical holes apart. Count from it.
Pick a pin to see where it goes. GND is the transistor's emitter: the buzzer's current comes back through it. VCC is the buzzer's own supply, and it goes to 5V on every board in this book. SIGNAL is the input: a 1 kΩ resistor and a transistor, nothing else. NC is in no net at all.
What HIGH means
The front prints ACTIVE HIGH beside the header and the back prints BEEPS WHEN GPIO IS HIGH. Both say the same thing: drive SIGNAL HIGH and it sounds, drive it LOW and it stops. There is no pitch to set and no library to load.
What neither says is what happens when nothing drives SIGNAL. The net list answers that: SIGNAL reaches R1 and nothing else, so there is no resistor holding it LOW. A floating SIGNAL is usually quiet, and a pin pulled HIGH while your board starts will sound the buzzer. Quiet at boot is about which pins do that.
Five volts on VCC
The buzzer is a 5 V part and VCC is its supply, so VCC goes to a 5V pin: the Uno's 5V, the 5V pin of an ESP32 or ESP32-S3 board on USB, or a Pico's VBUS. That is safe beside a 3.3 V board because VCC never reaches SIGNAL. 3V3 works too, a little quieter; five volts or three has the numbers.
When it does not work
The square pad. From the front, parts up and pins pointing down, it is the left-hand pin, and the order is GND, VCC, NC, SIGNAL. The back prints no pin names; turned over, the square pad is on the right and it is still GND.
No. It is soldered to a pad that no trace reaches, so it makes no difference either way. It is there so every TinkerBlock block has the same four-pin header and one cable fits all of them.
Yes. SIGNAL reaches a 1 kΩ resistor and the transistor's base, and nothing on the board joins it to VCC. The base holds itself near 0.7 V; your pin only ever pushes a couple of milliamps into it.
The buzzer, the transistor that switches it, and the three small parts around them.
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