The PC1555 is a powerful integrated circuit. Adding a few external parts to it can turn it into various types of timing signal generators, such as monostable and astable multivibrators. It has trigger, threshold, and control pins. Inputting a signal to the reset pin can stop the circuit operation easily. In addition, the output can sink current as high as 200 mA (maximum). So, it can be used to drive relays and lamps.