Audio alarm signal initiation device

[0003] (1) Field of the Invention

[0004] The disclosed invention relates to audio alarm signal devices. More specifically, the disclosed invention provides a device which gradually increases the volume of an audio alarm upon the initiation of the alarm.

[0005] (2) Description of the Prior Art

[0006] Almost everyone has experienced the startling effect of the initiation of an audio alarm, such as a fire alarm. Indeed, a startling effect is one feature of such alarms in that they are designed to immediately and convincingly warn of a dangerous or even life threatening condition. Audio alarms are also typically high volume alarms so that they can be readily heard above background noise. While these features of audible alarm signals are preferred in the majority of situations when a dangerous condition is to be signaled, there are times when a substantially instantaneous full volume audio alarm initiation is unwanted. For example, an individual who has a heart condition may not: want such a startling alarm initiation sequence for fear of creating undue stress. In addition, when precise operations are being performed, such as explosive material handling or a surgeon performing surgery, a full volume audio alarm signal initiation could have devastating or catastrophic consequences.

[0007] Examples of prior art alarm initiation circuits are shown in U.S. Pat. Nos.: 4,523,058; 4,219,799; 4,482,888; 4,237,448; 3,681,916; and 3,931,621. However, none of these prior art patents disclose the precise alarm initiation device taught by the instant application. For example, the '058 Patent (Stevens et al.) is not an automatic alarm device and does not appear to be designed with this feature in mind. Likewise, the '799 Patent (Weber) is not an automatic alarm device and can not produce more than two different sound intensity levels. The '888 Patent (Todaka et al.) does not produce different sound intensities upon alarm initiation but, rather, it varies the frequency of the waveform at the output. In fact, it appears to produce three different frequencies of sound, not four actual intensity levels as is taught by the instant invention. The '448 Patent (Weinberg) teaches a pager with an escalating audio alert signal level. However, this reference does not teach or suggest an alarm initiation device that can be easily reconfigured to vary alarm sound levels between soft and loud levels in any fashion, such as the device disclosed herein, which can be readily changed by simply changing the values of resistors within the device. The '916 Patent (Itoyama et al.) discloses an analog alarm initiation device, not a digital device such as the one disclosed by the instant invention. Accordingly, it suffers from the same limitation described above with respect to Weinberg, namely, it is limited to escalating alarm signals and cannot be reconfigured to allow for any initiation strategy. The '621 Patent (Rose) teaches a device similar to that disclosed in Yatomama et al., namely, an inflexible, analog alarm system.

[0008] Accordingly, an audio alarm signal initiation device is needed which could provide a gradual alarm initiation sequence.

[0009] The disclosed invention provides an audio alarm signal initiation device which progressively increases the volume of an audio alarm signal in discrete steps in a short, yet non-instantaneous time period. The disclosed device includes a multiple voltage-controlled oscillator, at least two dual-input positive-NAND gates, a shift register and a plurality of transistors and resistors. These components are configured into a circuit, which provides the disclosed audio alarm signal initiation device.

[0010] These and other features and advantages of the present invention will be better understood in view of the following description of the invention taken together with the drawings wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings and wherein:

[0011] FIG. 1 is a circuit diagram showing the components of the disclosed invention;

[0012] FIG. 2A is a graph of speaker output wave form of a prior art audio alarm signal; and

[0013] FIG. 2B is a graph of speaker output wave form for an audio alarm device initiated using the disclosed audio alarm signal initiation device.

[0014] Turning now to FIG. 1, the disclosed audio alarm signal initiation device 10 is shown. The device 10 includes two medium-scale integration (MSI) integrated circuits, IC1 and IC2, one small scale integration (SSI) integrated circuit, IC3, two capacitors, C1 and C2, four transistors, Q₁-Q₄, eight resistors, designated as R₁, R₂, R₃, R₄, and (4) R_B, and one switch, SW1.

[0015] The result of the circuit of FIG. 1 is the creation of a rapidly increasing audio output, which reaches a maximum unmodified audio output in about three seconds. The disclosed device is also readily resettable so that future alarm signals will exhibit the same rapidly increasing minimum to maximum audio behavior as any other alarm signal.

[0016] IC1 in FIG. 1, which in a preferred embodiment is a multiple voltage-controlled oscillator, such as a dual voltage-controlled oscillator (VCO), generates at least two identical five volt (5 V), fifty percent (50%) duty cycle square waves at pins 6 and 8. The square wave signal at pin 6 is generated only when pin 1 is driven to 5 V from the speaker drive circuit (not shown) when the alarm is to begin sounding. The other signal is always generated provided the indicated power levels exist at the indicated pins of IC1 (5VDC at pins 13 and 14, 2VDC at pin 12 and φVDC at pins 7 and 9). The capacitors included with IC1 between pins 3 and 4 and between pins 10 and 11 determine the frequency of the square wave output signals at pins 6 and 8 respectively. In the circuit of FIG. 1, C1 and C2 are 500 microFarad (μF)/5 V capacitors, which create a 1 Hz square wave.

[0017] The output signal at pin 6 of IC1 is provided to the input of a first NAND gate N1 at pin 5 of IC3. The output of this gate N1 at pin 6 of IC3 controls the “clocking” or action of IC2. IC2 is a 4 bit parallel-access shift register.

[0018] If the output signal at pin 6 of IC1, which is the input at pin 5 of IC3, ceases, then the output of NAND gate N1 on IC3 ceases to change. Consequently, the clock (CK1) on IC2 does not change. If this happens then the output of IC2 does not change and the speaker output remains at its current state (off, maximum, or somewhere in between, provided the square wave input exists at the speaker for the latter two).

[0019] The normal mode of operation of IC2 is shown in FIG. 1 with SW1 in the indicated position. When the square wave input comes in at pin 9 of IC2, the outputs Q_Bthrough Q_D“shift” right so that Q_Bbecomes the value of what Q_Awas before it was changed by the clock signal and provides a switch signal to transistor Q₂. Q_Cbecomes Q_B, etc. Output Q_Abecomes φV. The full logic function table can be seen in Tables 1 and 2, below.

[0020] As the single 5 V output from IC2 at pins 10 to 13 moves from pin 13 to pin 10, a switch signal is provided to each of the transistors Q₁through Q₄, in turn, and the respective transistor associated with the 5 V output is “switched on”, while the other transistors associated with the pins having φV are “switched off”. This allows current to flow in its collector circuit, i.e., through the speaker SPK1, through the resistor R₁, R₂, R₃or R₄as the case may be, through the transistor, and then to ground. Since R₁>R₂>R₃>R₄, the speaker volume will increase as the transistors Q₁to Q₄are “switched on.” It is noted that resister R₄may be eliminated from circuit 10, i.e., R₄=0, while maintaining the operability of circuit 10.

[0021] When the last transistor, Q₄, is “switched on”, the audio signal at the speaker becomes its loudest (original unmodified output). This means that the Q_Doutput (pin 10) of IC2 has become 5 V, which drives this transistor. This Q_Doutput is also the singular input to a second NAND gate N2 on IC3 at both pins 1 and 2 of IC3. The output of gate N2 at pin 3 of IC3 now becomes φV. This is the second input (pin 4) to the first NAND gate N1 on IC3. The result is that the output at pin 6 of the first NAND gate N1 of IC3 remains at 5 V for the duration of the alarm cycle. This causes the IC2 shift register to stop shifting. Thus, the alarm signal remains at its full volume until SW1 is pushed. SW1 is a reset switch which, when pushed for at least one second, will start the sequence over again. The circuit may be reset in mid cycle or reset for the next time the alarm sounds off if SW1 is pushed at the end of a given alarm cycle.

[0022] The following full logic function tables show the inputs and outputs of the integrated circuits used in the present invention.

[0023] The original prior art speaker output wave form is shown in FIG. 2A. The modified output wave form is shown in FIG. 2B.

[0024] The entire circuit shown in FIG. 1 can be added to any existing circuitry by putting all components on a modified board into an existing fire alarm housing using the appropriate insulating material, such as heat shrink tubing.

[0025] One specific application of this device can be for residential use in housing for the elderly where sudden loud noises can be undesirable. Another application is in hospitals or workplaces where intense concentration interrupted by sudden loud noises could have detrimental effects.

[0026] Of course, alternative embodiments of the disclosed device are contemplated by the invention. For example, one alternative design, which encompasses all of the above mentioned functions, may include many more than four drive transistors (Q₁-Q₄) and more than a single 4-bit parallel-access shift register so that the alarm signal seems to continuously increase in volume rather than increase in discrete increments. Furthermore, it may be desirable to have an audio increasing interval longer than 25 seconds for some applications, which would require the use of different integrated circuits.

[0027] In light of the above, it is therefore understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.