On Sat, Jun 6, 2026 at 3:05 PM Marco Guerini wrote:

Dear Mr Sousa,

I happened to find a 1959 article detailing a “Respiratory Carbon Dioxide Response Curve Computer” using K2-W op-amps in an HKR-type Manifold, plus a K3-J unit. The K-type passive plug-ins were of course used and modified as needed, as the accompanying photo will show. One (extreme right) appears to have been remade in Lucite, and it’s thus transparent.

The computer itself has a clear schematic available, attached below with the full article scans.

It uses, apart from more common circuitry, a triple-gang 100k ohm potentiometer to implement, in a single stage, a “dead-space calculator” in a “novel circuit for carrying out the operation of multiplying a function by a coefficient and adding a constant by this product”.

A block diagram provides an explanation of each amplifier’s function. An XY plotter would graph the output, which was an alveolar ventilation vs CO2 concentration plot, which was included in the article.

Kind regards,

- Marco Guerini

Analog computer simulation of  "Respiratory Carbon Dioxide Response Curve Computer " by J. Weldon Bellville and J. C. Seed. PDF Contributed by Marco Guerini (added 7-7-2026)