Warning chord sound producing apparatus including an integrated circuit

Claim 1

A warning chord sound producing apparatus, comprising: an integrated circuit including a memory for storing program data, a clock signal generator providing a plurality of clock signals with a predetermined frequency, microprocessor means for executing said program data, and at least two output ports outputting a low signal and high signal constructing square-wave pulse trains, said memory having a plurality of addresses, in one of which, one of said program data is stored providing an instruction so that said low signal and said high signal appear at one of said plurality of output ports; a semiconductor switching means, which is controlled by said square-wave pulse trains from said output ports of said integrated circuit, so that said semiconductor switching means produces a plurality of output signals; sound producing means, including at least first and second sound producing elements driven by said output signals from said semiconductor switching means, for producing a chord sound; said instruction of said program data determining one of said output ports for outputting of said low signal or high signal and for selecting a level of said low signal and high signal; said means for executing said program data executing said instruction in one of said addresses of said memory in order and one by one when said clock signal generator generates one of said clock signals such that one of said output ports outputs a part of said square-wave pulse trains and another one of said output ports outputs another part of said square-wave pulse trains; said square-wave pulse trains having a first and second square-wave pulse train signal component; said first square-wave pulse train signal component comprising a plurality of first unit pulse trains having a duration of a first unit period, which includes a first basic frequency and first harmonic frequencies which are a plurality of multiples of said first basic frequency, said second square-wave pulse train signal component comprising a plurality of second unit pulse trains having a duration of a second unit period, which includes a second basic fequency and second harmonic frequencies which are a plurality of multiples of said second basic frequency, a ratio of said first and second basic frequencies being a ratio of natural numbers so that said first and second basic frequencies define a chord; said means for executing said program data outputs, repeatedly, said square-wave pulse trains from said plurality of output ports, one period of repetition of said square-wave pulse trains being a duration of a chord period defined as a natural number of said first unit periods and second unit periods, respectively; and said semiconductor switching means including at least two transistors which are controlled by said part of said square-wave pulse trains and said another part of said square-wave pulse trains respectively, from said at least two output ports.