This alarm oscillator was found in the December 1974 issue of Radio Electronics magazine. The power transistor must be equipped with a good heat sink. The Frequency basically is given by C1.
This circuit is from Mullard documentation from 1969. Transistors support current equivalents. Output...
By activating S1 the relay closes its contacts only after a certain time interval that depends on C1....
The circuit shown is from National Semiconductor's Linear Applications Handbook published in 1994....