This circuit was found in a1980s Motorola documentation. The integrated circuit is from that time. The frequency depends on the crystal.
This flip-flop with neon lamps was found in a 1969 publication that deals precisely with neon...
This circuit is the version of the previous circuit with a single source. The transistors are...
Found in a Popular Electronics from the 90s, it applies to the old answering machines that used...