This photoelectric sensor that triggers a relay was found in an English book from 1989. The transistor is a general-purpose type, and the integrated circuit consists of an operational amplifier.
This circuit is suggested by Texas Instruments in old documentation. The components depend on the...
This circuit is primarily intended for the calibration of common radio IF steps using the...
We find this circuit in a technical documentation of 1976. The transistors can be the BD135 and...