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Wang LOCI-2 Circuit Board 1401A

The 1401A circuit board is primarily involved in generating and driving the display of the LOCI-2 calculator. The display system of the LOCI-2 is not multiplexed, meaning that there is separate decoder and driver circuitry for each Nixie tube. Included in the circuitry for each digit is a blanking signal, which causes the Nixie tube to be blanked. The blanked Nixie tube is used as a "cursor" indicating the location of the next digit to be entered. The ten digits of the display are driven directly from the corresponding digits of the working register of the calculator (the "W" register). A 4-bit counter is used for indicating the location of the decimal point, as well a decoders and drivers from the discrete Neon tubes used for the decimal point. Two drivers are also provided for lighting the special sign-indication Nixie tube, which can display only a "+" or "-" sign. Another four bit counter Binary-Coded Decimal counter exists on the board for use in selecting the digit to be blanked, as well as being used for other utility purposes.