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.
This circuit is from Popular Electronics from October 0, 1981. The diodes can also be 1N4004 and...
This switch or band selector for receivers was found in a Popular Electronics from the 1990s. The...
This circuit, published in 1978, can use any general purpose NPN transistor such as the BC548 and...