Leeds & Northrup Enclosed-switch resistance box model 4770
Figure 1: Leeds & Northrup Enclosed-switch resistance box model 4770. Front view.
Figure 2: Leeds & Northrup Enclosed-switch resistance box model 4770. Front top view.
Figure 3: Leeds & Northrup Enclosed-switch resistance box model 4770. Front corner view.
These were suitable for commercial power frequency a-c as well as d-c. Rotary switch decades. D-C resistance change from zero setting, measured across binding posts, dial settings +/- 0.11 percent + 0.01 ohm. When highest decade in use is 0.1, 1.0, 10.0, 100.0, and 1000.0, current rating is 1.6, 0.5, 0.16, 0.05 and 0.016 amperes respectively. Model number 477o with 2 dials and 99 ohm resistance.
The main application of these resistance box is to control the specific value of current to flow through the circuit. The advantage given by the resistance box is that the variable resistances are available at one point. If any circuit requires variable resistances, then there is no need of replacing the resistor.
The resistance box comes in a Molded Bakelite case. The switch studs are made of solid Nickle and lasts much longer than brass. They are placed on polished hard rubber top plates and mounted on polished mahogany cases.
KU's Department of Physics & Astronomy currently have 2 of these in possession.