We found this circuit in the October 1978 issue of Radio Electronics magazine. The magazine article describes its assembly. The circuit is a 6-digit circuit using components from the time.
We found this circuit in a 1990 documentation. The operational amplifiers are type 741 and the LED is...
We found this circuit on an Elektor from the 90s. The frequency is given by capacitor C1. The...
Found in National Semiconductor publication from the 1980s. This gain-100 circuit can be...