With this circuit found in an American documentation from 1969 it is possible to vary the selectivity (Q factor) of a tuned circuit. The operational is from that time.
This circuit was found in a Popular Electronics of the 90s. The output amplitude will be between...
This circuit generates sequence of pulses in order and times determined by the capacitors in pins...
This circuit was obtained from an English magazine from 1979, but can be easily assembled today...