Datasheet legend
Ab/c: Fractions calculation
AC: Alternating current BaseN: Number base calculations Card: Magnetic card storage Cmem: Continuous memory Cond: Conditional execution Const: Scientific constants Cplx: Complex number arithmetic DC: Direct current Eqlib: Equation library Exp: Exponential/logarithmic functions Fin: Financial functions Grph: Graphing capability Hyp: Hyperbolic functions Ind: Indirect addressing Intg: Numerical integration Jump: Unconditional jump (GOTO) Lbl: Program labels LCD: Liquid Crystal Display LED: LightEmitting Diode Liion: Lithiumion rechargeable battery Lreg: Linear regression (2variable statistics) mA: Milliamperes of current Mtrx: Matrix support NiCd: NickelCadmium rechargeable battery NiMH: Nickelmetalhydrite rechargeable battery Prnt: Printer RTC: Realtime clock Sdev: Standard deviation (1variable statistics) Solv: Equation solver Subr: Subroutine call capability Symb: Symbolic computing Tape: Magnetic tape storage Trig: Trigonometric functions Units: Unit conversions VAC: Volts AC VDC: Volts DC 


"Hi there,", says the man on TV, "I want to talk to you about ducts." So begins Terry Gilliam's Orwellian satire, the movie "Brazil". An odd movie it is, but the same can be said about the Carrier Ductronic, one of the oddest calculators I've ever seen.
The primary function of this calculator is to assist the design engineer in sizing air conditioning ducts. For instance, the air velocity, corrected for friction, in a circular duct with a diameter of 12 inches and an overall airflow of 500 cubic feet per minute (cfm) can be calculated using the following keystrokes:
CLR D 12 Q 500 V =
In response, the calculator displays 636 (feet/minute, duct velocity.)
Printed on the back of the calculator is a table of fitting loss coefficients (i.e., coefficients that describe what happens in a duct at an elbow or junction.)
Pressing the CAL button puts the device into regular calculator mode, where it can serve as a basic fourfunction calculator with square root. It has a few oddities: for instance, it calculates square roots only to three decimal digits of precision. When entering numbers, if you key in more than 8 digits, the calculator exhibits all kinds of strange, buggy behavior.
Had it not been for the fact that just last year, I was working on a software package for a humidification equipment manufacturer, this device would surely have escaped my attention. I wonder: are there many other similar specialpurpose calculating devices out there? In the 1960s and before, sliderule or circular sliderule type special purpose calculators (made of wood, plastic, or even more often, cardboard) were quite common. Such electronic calculators, however, appear fairly rare.
Of course, the Ductronic's functionality can easily be replicated on most programmable calculators. Nevertheless, it is an interesting piece that I happily added to my collection of oddball calculators.