This circuit with germanium transistors is from 1960 and was found in Mullard's transistor application manual from 1960. The circuit can be adapted to use more modern transistors.
I found this circuit in a Popular Electronics from November 1999. The magazine is no longer...
This circuit, from a Motorola manual, uses transistors from the time, but can be implemented with...
This circuit was found in a 1986 publication. The speed of the effect is determined by the 555,...