This TTL circuit is from a Radio Electronics magazine from February 1973. The circuit must be powered with 5 V and the maximum frequency depends on the TTL integrated circuit.
This circuit was found in a 90s Wels' Think Tank. The frequency depends on C2 and R3. The handset...
This circuit was obtained in a March 1995 edition of the American magazine Electronics Now. The...
This circuit was found in a 1992 Electronics Hobbyst Handbook. The circuit is for the 110 V power...