Telephone dialer (CB8521E)

Using an integrated circuit from the time, we found this configuration in a 90s Radio Electronics.

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Proximity Relay (CB25343E)
This proximity relay circuit was found in the July 1990 Radio Electronics magazine. The supply...
Pulse Width Modulator (CB5364E)
This circuit is from an old operational amplifiers manual. However, the setting applies to modern...
Sine to square converter CA3140 (CB24971E)
Using an operational amplifier, the figure shows how to convert the waveform to low frequency...