This lockable two-position servo control system was found in documentation from the 1990s. The error amplifier can be an operational amplifier and the sensors are phototransistors.
This circuit was found in a 90s Radio Electronics. It is intended to amplify the sound channel of...
This circuit uses a 4020 counter that divides the frequency up to 210, being found in a former...
This circuit was found in a Radio Electronics magazine from May 1967. The circuit has the time...