ZNP500 light activated photoswitch by Ferranti. Package: 8-pin glass windowed TO-5 Originally produced by Ferranti for Horstman Gear Co. of Bath (UK) as part of a £70,000 street lighting project in 1973. The C.D.I (Collector-Diffusin-Isolation) chip consists of a photodiode, an 18-stage counter controller logic circuit, series and shunt regulators and a thyristor driver stage , impressive or what ! When the illumination falls below 70lx, the circuit causes the street light to turn on. A built in timer with a delay of 30s ensures that transient light changes such as lightning are ignored. The unit switches of when illumination rises to 35lx provided that the lamp has been on for about one hour. It was estimated that this circuit could save 100 hours of electricity per year per lamp compared to other photocontrols. Datasheet needed ! has anyone got one please ? Status: NOS (new Old Stock). (some with gold plated leads as in photo, some with plain nikel plated leads, these being of a later manufacture - 1980's) RoHS compliant: no