This circuit is from a 1968 documentation using one of the first integrated circuits available at the time, the TAA370. The circuit is powered by 1.3 V using a 200 ohm handset.
We found this circuit in a 1994 publication. It makes use of a divider for 16 384 CMOS type 4060. By...
This circuit was obtained in an old Elektor. It is a reference, since the integrated products of the...
Figure bellow shows another circuit that allows adjustments in the duty cycle of the output...