This circuit was found in the October 1983 Radio Electronics issue. It is applicable to old analog telephones. The circuit uses common components.
Found in documentation from the 1980s, this circuit can generate signals in a range that reaches a few...
Found in a 1967 publication by General Electric, this control is intended for motors up to 2 A...
This circuit was found in a 90s Popular Electronics. The circuit uses components from that time,...