Largely analogue electromechanical voice calculator

Something i need to get out of my head. I was hoping it would come out in a more coherent and organised manner but frankly, i simply lack the knowledge and ability to flesh this out any more than i have, so as usual i’m just going to dump it here.

This is a partly analogue electromechanical device for performing simple calculations. To the user, it appears to consist of an intercom with a button, a box and a speaker. The user operates it by pressing the button, speaking a digit, releasing the button and repeating until the end of the first number is reached, pressing another button to enter the number, repeating the process for the second number, then speaking the operation to be performed and entering that in the same way: “add”, “subtract”, “multiply”. The digits of each number are spoken from the least to the most significant and are assumed to be positive.

This next bit is somewhat like the IBM Shoebox, and my extreme ignorance of electronics is probably about to show. In fact, right now i am quite shockingly unable to remember anything, so this is not going to be good.

As each number is spoken, three analogue filters analyse the sound in terms of whether it includes periods of near-silence, white noise or relatively pure low, middle or high tones. The exact pattern also depends on accent. Some words have one syllable, others two, giving them a different shape - a single sound which is relatively loud or two sounds separated by a relatively quiet interval.

It seems to me that the different features which need to be detected would be: High pitch on a relatively pure tone, low pitch on a pure tone, maintained pitch on a pure tone, noise rather than purity, a period of near-silence and a period of relatively low sound intensity between two periods of relatively high sound intensity. I also suspect that these features can be detected by analogue means.

The start and end of an utterance do not need to be detected because they are simply achieved by pressing the button on the intercom, that is, turning on the machine which detects the sound of the digit and turning it off. This would probably need careful timing.

My accent is non-rhotic, near-RP British English most of the time and this assumes a similar style of speech, though similar things could be done with other accents.

It seems that the digits differ as follows, in my accent at least:

Zero: High pitch, decreasing intensity (i.e. two syllables), low pitch. One: Low pitch, higher pitch, low pitch. Two: White noise, low pitch. Three: White noise, high pitch. Four: White noise, low pitch. Five: White noise, rising pitch. Six: White noise, high pitch, silence, white noise. Seven: White noise, high pitch, decreasing intensity, high pitch. Eight: High pitch, silence, white noise. Nine: Low pitch, rising then falling.

Except for “two” and “four”, each of these is different and a series of capacitors of different capacitance would lead to appropriate delays and timings. I suggest, therefore, that for this example, “four” is pronounced with two syllables: White noise-low pitch-decreasing intensity-middle pitch. Then it goes digital. Each of these can be plugged into some logic gates to give unique results. I wish this bit could be analogue too: maybe it can be.

The digit, i.e. the output of the network of logic gates, is converted into a voltage of the appropriate level, ten times more with the second press, grouped into threes, so there are a series of currents but it doesn’t get ridiculously intense. An “overflow” is then added into the next set of circuits and reduced by a factor of ten. These are again stored somehow.

The next set of digits is stored in a second set of the same components. The “enter” button switches over to this set.

Finally, the user speaks one of the three words “add”, “subtract”, “multiply”, words of one, two or three syllables, easy to distinguish, and presses a second “enter” button. This analyses the words similarly and does one of the following:

Add: combines the voltages to produce an appropriate output. Subtract: switches the second voltage over to its negative equivalent. I have no idea if that’s feasible. That is then combined with the other voltage to produce a difference. Multiply: Adds repeatedly while reducing the other voltage until it reaches neutral.

Finally, somehow (again), this is turned into a series of pulses which drives a stepper motor which moves a stylus along a wax cylinder with a series of grooves. Each groove contains a recording of a single digit being spoken once. Each is played, then the stylus returns to the start, then the next digit is found in the same way and played. These recordings come out via a trumpet similar to that on a conventional record player.

So, to summarise, it goes: electronic analogue, electronic digital, electronic analogue, mechanical.

Could possibly be simplified by allowing a “Morse-code” style input and output and binary addition, subtraction and multiplication.