Cordless doorbell red 230V AC P5750 battery free

Product - wireless doorbell
Outdoor range - 150 m
Number of sound levels - 10
Binding method - automatic
Signal - optical , sound
Maximum sound intensity - 110 dB
Possibility to add buttons - yes , 3 max
Waterproof button - yes
Volume control - yes
Transmit frequency - 433 MHz
Colour - white , red
Clock power supply - 230 V

Button does not require battery ( batteries )

The button connects to the clock via radio waves at a frequency of 433,92 MHz. And it can be done without batteries. How can the button work without batteries? The energy to send a signal to the clock is generated by pressing the button. A simple and functional solution.