This project is also based on Jaycar’s Secret Farter. After you’ve had your fun with it, turn it into something useful – a wireless doorbell. You can place the doorbell receiver anywhere in your house or backyard so that it can be easily heard where you are located.

There are plenty of times when it is impossible to hear if the doorbell rings. You may be entertaining or just relaxing and miss hearing someone is at the front door. In fact, it is often invited guests who have the most trouble in making their arrival noticed. A wireless doorbell can help solve this.

Fig.8: the Doorbell Sounder is based on a 7555 to produce a Ding Dong tone.