The transistors of this circuit found in a 1965 magazine can be the BC558 and the sensitive 12 V x 50 mA relay. The other components are common.
This small signal injector generator was found in the February 1971 issue of Radio Electronics magazine....
This circuit that generates signals between 1.5 and 2 kHz was found in a documentation from the...
Other operational Amplifiers in the series, such as the MC34072, MC34074, MC35071, MC35072,...