Many integrated circuits have undocumented features or abilities. This is one of them. The TLC555 output (pin 3) can sink a 100mA load to 1.28V. The open drain transistor reset (pin 7) can sink 100mA ...

The essence of the circuit is for the input of tone and signal to provide an activation for the relay switch. Relay – an electrically operated switch where the current flowing through the coil of the ...