This circuit was found in a 80's Popular Electronics. The sensor can be any phototransistor. The circuit is indicated for an audio link modulated in pulses.
This protection circuit applies to booster steps for the 78xx series integrated units where xx is...
The transistors of this 12 V x 150 mA power source can be BC558 for PNP and BD135 for NPN. The...
We found this circuit in a 1977 Radio Handbook. The lamp is the critical component, being 120MB at the...