LM317 DIY Kit Adjustable Voltage 220V to 1.25V-12.5V Step-Down Adapter PCB Module Electronic Kit

Single-sided adjustable signal generator output. Convenient to provide pulse signal
With a logic pen function. To the convenient logic of the test circuit
With disposable buzzer You can turn the wires on and off (connect the wires to positive power and signal input, wires to summer sound).
You can also test the low frequency signal (insert the signal from the signal input, if there is a signal, the sound of the buzzer)