Wang LOCI-2AC 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 National NL-8421/5092 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.
Our LOCI-2 was shipped as a model 2AC, so it has 16 Storage Registers in core memory and a 1412A Teletype interface. It doesn't have a 1407 Storage Register board because it is a model 2A and has a 1410A 16 Storage Register board instead.
Our LOCI-2. #3026, came from the Wang Connecticut Customer Engineering office. It was used in the late 60’s and early 70’s as a test bed and repair kit for field service engineers. If they couldn’t repair a board in the field the defective board was sent to the Wang home office and exchanged for a functioning one. We also received a salesman's case containing a complete set of spare boards, a card reader, and a complete keyboard.
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-2 calculator are:
1501 Input Decoder Control for the Card Reader and Teletype
1401A Register Decoder and NIXI Display
1402A W-Register with Binary Adder
1403B L-Register with Binary Adder
1404A Main Timing
1405A Miscellaneous Shift Pulse and Control
1406A A-Register with Accumulator, Decimal Counter
1408A Program and Decrement Counters plus Storage
1412A Teletype Input and Output Control
1410A 16 S-Registers Containing 10 Digit Decimal + Sign of Each Register (Core)
There are a few LOCI-2 calculators left, most in private collections. These are the public ones: