This simple low power triplicator was found in 90’s American documentation. The diodes can be general purpose types and the frequency is determined by the RC network of the 555.
The circuit is from an 80's publication, but the components are current, only special type diodes...
This alarm circuit is from a 1990 Electronics Handbook. Transistor Q1 can be a BD135 and the relay...
We found this circuit in the Texas Instruments opto-electronics manual. The FET admits equivalent as...