Found in American documentation from the 90's, this circuit applies to other operational amplifiers. The frequency can be changed by changing the components.
This is a Serial In - Parallel Out or Serial Out [SIPO or SISO] shift register using the...
This circuit was obtained in a 1973s documentation. The transistors may be BC558 for the PNP and...
This circuit was obtained from a 1978 Practical Wireless. It causes an LED to flash at a frequency that...