Full Size Original
Hollerith Tabulator Dial
The 1890 Hollerith tabulators consisted of 40 data-recording dials. Each dial represented a different data item collected during the census. The electrical impulses received as the reader's pins passed through the card into the mercury advanced the hands on the dials corresponding to the data contained on the punch card (i.e., responses to inquiries about race, gender, citizenship, age, etc). When the bell signalled the card had been read, the operator recorded the data on the dials, opened the card reader, removed the punch cards, and reset the dials.