These boxes are commonly used in an electronics development lab to select the resistor or capacitor value that's most suitable for a circuit being developed. They contain a full range of precision value resistors ranging from single digits up to millions of ohms, any value of which can be selected by the rotary switches. In use, the box is connected with wires into the appropriate place in the circuit & the knobs cautiously adjusted until the circuit is working to the optimum as might be observed by an oscilloscope or counter also connected to the circuit. Once the optimum value is determined then an appropriate fixed value component is substituted. Of course we also do a wide range of oscilloscopes, frequency counters under our laboratory category.
Top right box is the most contemporary. The yellow box is good for 1980s or later. The turquoise boxes are 1960s-1970s.
Prop ID: 2125