Exhibit 189 is a resistance box with 16 brass keys whose removal inserts into the involved circuit a resistance from 1, 2, 3, 4, 10, 20, 30, 40, 100, 200, 300, 400, 1000, 2000, 3000, or 4000 Ohm, respectively. A similar device is exhibit 180.
ISCRIZIONI
Sul lato dell'apparato è attaccata una tabella ohm/amp
