Forced simultaneity applied to a calculator impossible
If you have ever watched an expert operator using a “Comptometer,” try to imagine that operator hesitating to select a group of keys and depressing them exactly simultaneously as one is compelled to do on one of the key-driven cash registers. And then, on the other hand, if you have ever seen a key-driven cash register operated, try to imagine its being operated at the lightning speed at which the “Comptometer” is operated.[4]
It must be understood that the exact or forced simultaneity of the cash register scheme, if applied to a calculating machine, would lock the whole keyboard if one of any of a group of keys the operator wished to strike was depressed ahead of the others, and would thus prevent the rest of the group from being depressed until the return of the first key.
Flexible simultaneity of key-action a Felt invention
It is within reason that a locking action of that character would even defeat the speed of key-action that was possible on the old “Comptometer,” since an operator could overlap the key strokes in that machine to a certain extent; whereas the forced simultaneity of the cash register, if applied to the “Comptometer,” would prevent any overlapping or the depression of a second key until the first depressed key returned.
The only simultaneity of key-action that could provide a means of speeding up the old “Comptometer,” or any machine of its type, was a means that would leave key-depression free as to matter of time; one that would be perfectly flexible in group manipulation, offering a complete fluidity of motion such as not to hinder the fingering of the operator.
The purpose of the mechanical means employed to give simultaneity in the cash register was to lock all the keys depressed together and lock all others against depression until the former returned. The purpose of mechanical means employed in the Felt patent was to give perfect freedom of key-action, whereas formerly the key manipulation of the old “Comptometer” was restricted in the freedom of key-action, to the extent of being limited to seriatum action.
The above discussion has been somewhat elaborately detailed to offset statements that simultaneity was old in the key-driven Art. There is no question as to the cash register type of inflexible simultaneity of action being old before Felt patented his flexible type of simultaneity of key-action for a key-driven calculating machine; but any statement intended to convey the idea that Felt’s contribution of the flexible simultaneity of key-action to the Art was not new, must come from ignorance of the facts or malice aforethought.
Duplex Comptometer
This flexible keyboard “Comptometer” was given the trade name of “Duplex Comptometer;” the term “Duplex” meaning that two keys could be depressed, as distinguished from the seriatum one at a time key-action formerly required. The term, however, fell short of setting forth the capacity of such action, as it was, in fact, not restricted to mere duplex-action—it was really a multiplex key-action having no limit except the lack of fingers on the part of the operator to depress the keys.