Range Extender for Door Bell
This device is used to extend the range of a cheap 433MHz (OOK) doorbell. It only needs to be placed between the sender (door button) and the receiver (bell), whithin the range of each.
It waits to get a specific button code from the 433MHz receiver, then waits a second before sending the code to the 433MHz transmitter. The delay prohibits, that the two rf signals overlap.
This can also be used to replace a defective door button or bell. In such a case, the repeater can replace the received code with the correct code for the bell.