US 4,727,331 A · Warning tone signal generator

Abstract

Pulses of constant pulse frequency but varying duty cycle are generated in a pulse generator which provides pulse trains or pulse sequences, as controlled by a pulse train or pulse length or sequence control unit coupled to the pulse generator and controlling the pulse generator to emit a train or sequence of pulses of similar pulse lengths, and further including a pulse length modulation control unit (12) coupled to the pulse generator and to the pulse train or sequence control unit, to control the length of the pulses of the individual pulse trains, the pulse lengths increasing in sequential pulse trains to provide an output signal of increasing intensity. The output from the pulse generator is filtered with respect to the base frequency, for example 800 Hz, and generated square wave pulses are converted into sawtooth wave pulses by a RC circuit to increase the dynamic range of output obtainable. The pulse generator (10), the pulse train length control unit (11) and the pulse length modulation control unit (12) can all form part of a digital microprocessor, generating the pulses, with intervening intervals to provide for a warning tone rhythm, the intervening intervals permitting the microprocessor to carry out calculating functions other than pulse generation for the warning tone.

Claims19

Dependent claims

Tone signal generator, particularly warning tone generator to provide a tone rising in intensity during the occurrence thereof comprising

a digital pulse generator (10) providing pulses of constant pulse repetition frequency and of a controlled varying pulse length, or duty cycle;
a pulse train or sequence control means (11) connected to and controlling the pulse generator (10) to control emission of the pulses in sequential grouped trains or sequences of pulses in which the pulses of any train, or sequency are of similar pulse length and the number of pulses, in any train as well as the pauses between sequential pulse trains are controlled by said pulse train or sequence control means,
said pulse trains and pauses defining the repetition of the warning tone;
a pulse length modulation control means (12) connected to and controlling the pulse generator (10) for selective control of the length of the pulses in respective sequential pulse trains or sequences, to provide for at least one pulse train subsequent to a prior pulse train in which the length of the pulses in said subsequent pulse train is longer than the length of the pulses of the preceding pulse train;
a filter (13) tuned to the frequency of the pulses in the pulse trains or sequences connected to receive the pulses from the pulse generator (10) and providing said tone signal;
and
wherein the pulse repetitoin frequency provided by said tone generator is the frequency of the tone signal.

4 more elements

Method of generating a warning tone of increasing level in a warning tone generator, comprising the steps of

(a) counting clock pulses at a first counting rate (50 kHz) to a first predetermined number to determine the number of pulses in a pulse train;
(b) counting clock pulses to a second predetermined number to determine an initial length of the pulses in said pulse train,
and generating an "end of pulse" signal when said second predetermined number is reached;
(c) continuing counting clock pulses up to a predetermined maximum number corresponding to the maximum pulse length and a minimum pulse gap for any pulse-pulse gap combination,
wherein the predetermined maximum number corresponds to a maximum pulse length and a minimum pulse gap length counted at said rate of clock pulses (50 kHz) to result in a pulse repetition frequency corresponding to the frequency of said warning tone;
(d) generating a carry condition pulse when said maximum number is counted;
(e) applying said carry condition pulse to an output terminal of the warning tone generator;
(f) repeating the steps c;
d;
e until said first predetermined number is reached,
whereby a pulse train will comprise pulses of a length being a function of said second predetermined number and of a repetition rate being a function of said maximum number;
(g) counting clock pulses at said first counting rate (50 kHz) to a third predetermined number to determine the length of pauses between pulse trains;
(h) incrementing said second predetermined number to increase the length of the pulses in said pulse train;
then repeating steps a-g
(i) whereby a pulse train comprising the pulses of a length which is a function of the incremented second predetermined number and of the repetition rate which is a function of said maximum number is obtained,
and wherein the resulting warning tone will be pulses of increasing amplitude due to the longer pulse, but of the same frequency, or pitch due to the coounting at said same rate to the same maximum number.

13 more elements

Dependencies are inferred from the claim text.

Warning tone signal generator

Life of this patent

Warning tone signal generator

Life of this patent

Abstract

Claims19