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Multi-frequency busy signal synthesizing circuitry

  • US 4,421,952 A
  • Filed: 10/16/1981
  • Issued: 12/20/1983
  • Est. Priority Date: 10/16/1981
  • Status: Expired due to Fees
First Claim
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1. Circuitry for synthesizing a tone output signal that approximates a multi-frequency signal comprised of a first tone having a first predetermined frequency and a second tone having a second predetermined frequency, said synthesizing circuitry comprising:

  • a signal source for generating a clock signal having a predetermined frequency that is greater than said first predetermined frequency and said second predetermined frequency;

    means for generating a control signal alternately having first and second states at a frequency that is substantially one-half of a frequency selected from a predetermined range of frequencies substantially midway between said first predetermined frequency and said second predetermined frequency; and

    means coupled to the clock signal source and generating means for dividing the clock signal by a first number in response to the first state of the control signal to produce the tone output signal having a first frequency greater than said first predetermined frequency and by a second number in response to the second state of the control signal to produce the tone output signal having a second frequency that is greater than said second predetermined frequency.

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