Wang LOCI-2A Calculator
Logarithmic Calculating Instrument

The Wang LOCI-2 Programmable Calculator was introduced in January 1965, replacing the LOCI-1 that was introduced just four months before. The LOCI-2 has more than 1,000 transistors, no integrated circuits, core memory, and Nixie Tubes for the display. To dramatically improve the speed of multiplying and dividing it actually added or subtracted logarithms. It supported a printer, Teletype, and punched card reader peripherals.

This LOCI-2 is a model 2A, so it has 16 Storage Registers instead of 4 on the model 2, and no I/O interfaces.

This LOCI-2. #2814, was donated by Tom and Ingrid Barry. It was originally purchased by the GTE Sylvania Lighting Products Group in Danvers, Massachusetts.

Numbers are stored in the registers in Binary Coded Decimal format. There is a 1, 2, 4, and an 8 bit for each digit in a number. The decimal value of a digit is the sum of the bits for each weight, e.g. a 9 is stored as a 1 and an 8. Each bit is stored in a flip-flop made from two transistors. Most registers are 10 digits wide, so it takes 2 x 4 x 10 = 80 transistors to make a register.

The boards in this LOCI-2A calculator are:

  1. 1501 Input Decoder Control for the Card Reader and Teletype

  2. 1401A Register Decoder and NIXI Display

  3. 1402A W-Register with Binary Adder

  4. 1403B L-Register with Binary Adder

  5. 1404A Main Timing

  6. 1405A Miscellaneous Shift Pulse and Control

  7. 1406A A-Register with Accumulator, Decimal Counter

  8. 1408A Program and Decrement Counters plus Storage

  9. No connectors or wiring harness

  10. 1410A 16 S-Registers Containing 10 Digit Decimal + Sign of Each Register (Core)

The restoration blog is here.

There are a few LOCI-2 calculators left, most in private collections. These are the public ones:

Wang LOCI-2 Model 2A