Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Central Scientific Company
Humboldt College; c.1950
"Designed especially for use in elementary work." This box would be used as a standard resistance in laboratory work in schools. Resistance values, to 0.2%, are adjusted by removing the brass pegs. The box is constructed with the pegs in parallel with precision bifilar wound resistance coils-with the peg in place the current flows through the peg ( 0), when removed the current flows through the resistor.
The instrument is contained in a one piece cast bakelite case, the top of which has been ground flat. The binding posts are of polished brass with captured knurled nuts. The resistance value is adjusted by inserting plugs (tapered brass with black bakelite handles) into holes connecting brass lugs which are embedded into the top surface of the case. The total resistance of the box is 11,100 ohms divided as follows: 10, 20, 30, 40, 100, 200, 300, 400, 1000, 2000, 3000, & 4000. The name Cenco is engraved into the top center of the case. The name and resistance values are all white filled. There is a red ink stamp near the binding posts, consisting of a circle within a circle and the figures c.s. / 1 inside the center circle. The bottom of the case is covered by a perforated aluminum sheet, held on by four brass screws at the corners, u.s. pat. 1,781,802 is ink stamped in black 1/2" figures across it.
A similar instrument is shown on p 1300 of the 1950 Cenco Catalog (J150) as item 82785. The illustration appears to show a black box with brass binding posts as well. The 1960 (J-300) Cenco Catalog shows plastic binding posts and grey plugs for this instrument (P 758, item 82785).
© R. Paselk