Found in a Popular Electronics from the 80's, this circuit makes use of a time integrated to control a relay in a timed way. R2 determines the activation time.
The phototransistor of this alarm can be of any type. The relay must be sensitive type according...
This circuit was found in an American documentation from 1969. Indications of the used transistors are...
Information about the high voltage transformer and the detecting circuits was not given in this...