Found in a 90s Elektor, this circuit makes use of general-purpose transistors, except T4 that can be replaced by an equivalent.
This circuit was found in an old European documentation. When R2 is cut off the circuit triggers...
This circuit is from an 80's documentation. It makes use of two SCRs with current capacity...
This circuit makes use of a PLL 567 to invert the phase of a signal, ie to change it from 0 to 180...