The Door Bell old solution is the ASK modulation, they are unstable for signal process and inteference, sometimes in the night, the bell maybe "ring" "ring", now we use the low cost Semtech chip to design the good doorbell product, for example the Honeywell the 5 gen. door bell are use the Semtech chip or module solution. And LJ is the Chip/Solution provider.

Chime/push-button doorbell with wireless, plug-in power supply
Easy, do-it-yourself installation
3 chime settings and flashing light for clear notification
16 codes available to prevent interference from other users