This light meter circuit was found in 80's Radio Electronics. The circuit uses a milliammeter as an indicator and the sensor is a common LDR. The power supply must be symmetrical.
Found in Unitrode documentation from the 1980s, this circuit makes use of PUTs, currently common...
This simple circuit with SCR and unijunction transistor appeared in Radio Electronics magazine in July...
This TTL generator that can function as a control shield or external clock for microcontrollers was found in...