Listening to calls from a mobile phone is a very common problem in the elderly. Presbycusis, or hearing loss, occurs in most people as they get older, but it also happens with younger people, when they are exposed to sounds that are too loud for a long time.
Looking a bit in the 'Play Store', you can find many applications that allow you to turn on your phone's flashlight when you receive calls or messages on social networks ... and all this is configurable!
This simple circuit allows the connection of a big acoustic buzzer or the lighting of an auxiliary light, each time your mobile phone receives a call. In addition, the base has a power suply to charge the mobile phone when it is supported on the base.
M3 insert nuts are needed to close the box and hold the PCB (minimum 8).
Information in spanish