Using this circuit diagram and few electronic components can be designed a circuit which generate both visual and audible warning. When the CMOS inverters IC1b IC1a forms a bistable open / closed, activated by the touch sensor, and the R1 provides a positive reaction so the circuit will be locked in the state was left.
Bistabil output control IC1c-IC1d astabil which is designed to oscillate at a frequency of about 11 Hz. This frequency is determined by R2 and C1.
When the sensor is touched ON, the LED lights up and buzzer sounds intermittently.