Fix a Wireless Doorbell with ESP-NOW

One of my long-waiting outstanding projects is to fix this no-frill SoundTech doorbell. I finally done it, by replacing the RF transmitter/receiver used by the doorbell with ESP-NOW. The Problem with SoundTech doorbell The doorbell is a wireless one, operated on a unknown frequency band, presumably on 403MHz band or even 27MHz band. The indoor [ ]