The recognizer discussed will automatically recognize telephone‐quality digits spoken at normal speech rates by a single individual, with an accuracy varying between 97 and 99 percent. After some preliminary analysis of the speech of any individual, the circuit can be adjusted to deliver a similar accuracy on the speech of that individual. The circuit is not, however, in its present configuration, capable of performing equally well on the speech of a series of talkers without recourse to such adjustment.
Circuitry involves division of the speech spectrum into two frequency bands, one below and the other above 900 cps. Axis‐crossing counts are then individually made of both band energies to determine the frequency of the maximum syllabic rate energy with each band. Simultaneous two‐dimensional frequency portrayal is found to possess recognition significance. Standards are then determined, one for each digit of the ten‐digit series, and are built into the recognizer as a form of elemental memory. By means of a series of calculations performed automatically on the spoken input digit, a best match type comparison is made with each of the ten standard digit patterns and the digit of best match selected.