GB2126391A

GB2126391A - Audio warning system for a door or window

Info

Publication number: GB2126391A
Application number: GB08323777A
Authority: GB
Inventors: Marcel Valier-Grossman
Original assignee: VALIER GROSSMAN MARCEL
Current assignee: VALIER GROSSMAN MARCEL
Priority date: 1982-09-07
Filing date: 1983-09-05
Publication date: 1984-03-21
Also published as: GB8323777D0

Abstract

An audio warning system for a door or window has a switch trigger arranged to provide an output signal when the door or window is illicitly opened and which is connected to a loudspeaker noise source that is mounted in a hollow portion of the door or window. The loudspeaker noise source utilises the resonant structure of the enclosing walls of the door or window to amplify the sound produced thereby. A keyboard is provided so that a personal identification may be inputted to disable the loudspeaker noise source when an authorised person opens the door or window.

Description

SPECIFICATION Audio warning system for a door or window This invention relates to an audio warning system for a door or a window and to a system including such a door or window.

It is known to employ an electrical switch which is operable when a door or window is opened in an unauthorised manner and to connect the electrical switch to a noise producing source such as a bell or loud speaker which is separately located in the room connected with the door or window. However, such systems have the disadvantage that, although a noise is emitted immediately upon unauthorised use of the door or window, once a trespasser is inside the room it is very simple for him to disable the noise source by cutting the power supply thereto or by simply breaking the noise source.

The present invention seeks to provide an audible warning system which may be utilised with a hollow door or window frame structure in which the foregoing difficulty is at least partially mitigated.

According to one aspect of this invention there is provided an audio warning system for a door or window including trigger means arranged to provide an output signal when the door or window is elicitly opened, noise source means connected to the trigger means and arranged to be mounted in a hollow portion of the door or window, said noise source means comprising means for producing electrical signals to drive a sound producing means, wherein, in operation, the enclosing walls of the door or window are utilised as a resonant structure to amplify the sound produced by said sound producing means.

Preferably, the sound producing means is chosen from one of a loudspeaker, buzzer or an air horn.

Conveniently, the means for producing electrical signals is an electrical circuit similar to that found in Geemarc Model No. 808, that is, the means for producing electrical signals includes a latching and oscillator enable circuit connected to be energised by the trigger means and to provide an output to drive an oscillator which is arranged to drive the sound producing means.

Preferably a plurality of keyboard switches each marked with differing indicia are connected to an indicia code identifier which is in turn connected to the latching and oscillator enable circuit, whereby an identification code is pre-programmed into the code identifier and the latching and oscillator enable circuit is disabled upon the correct code being entered on the keyboard switches.

Conveniently a delay circuit is interposed between the trigger means and the latching and oscillator enable circuit.

Advantageously, the trigger means is a plunger actuated switch, or a magnetic reed switch, or a vibration switch, in each alternative, said switch is operable to actuate the noise source means.

According to a further aspect of this invention, there is provided an audio warning system including a hollow framework of a door or window, trigger means arranged to provide an output signal when the door or window is elicitly opened, noise source means connected to the trigger means and arranged to be mounted in the hollow portion of the door or window, said noise source means comprising means for producing electrical signals to drive a sound producing means, wherein, in operation, the enclosing walls of the door or window are utilised as a resonant structure to amplify the sound produced by said sound producing means.

Preferably, the noise source means is mounted in the outer frame of the door or window defining the door or window aperture.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows, in schematic form, a horizontal cross-section through a door frame; Figure 2a shows, in schematic form, a plunger switch with the door closed; Figure2b shows the plunger switch of Figure 2a with the door opened; Figure 3a shows a magnetic reed switch in schematic form with the door closed; Figure 3b shows the magnetic reed switch of Figure 3a with the door open; Figure 4a shows a vibration switch in a non-alarm position; and Figure 4b shows the vibration switch of Figure 4a in an energised, alarm producing mode; Figure 5 shows in block schematic form the electrical circuit of the system.

In the Figures like references denote like parts.

The audio warning system, shown in Figure 1, has an upright limb of the aperture defining aluminium extruded frame 1 of a door within which is mounted an electrical circuit 2 and battery power supply similar to that found in Geemarc Model No. 808 for producing electrical signals to drive a loudspeaker 3.

The frame will have a secreted portion for replacement of the battery. The arrangement for triggering the electrical circuit 2 is not shown in Figure 1 for clarity. The frame 1 is not necessarily a complete enclosure containing air since any opening 4 in the framework can be employed as a means of providing a Helmholtz resonator to amplify the noise radiated by the loudspeaker 3.

Although a loudspeaker is shown in Figure 1 this may be replaced by a buzzer or an air horn.

The loudspeaker is located within the enclosure formed by the framework in the optimum position and direction to drive the acoustical and structural resonances of the door frame elements. The air enclosed in the frame 1 has characteristic resonances determined by the physical dimensions of the enclosure. At the natural frequencies of the cavity, noise radiated by the loudspeaker 3 will be amplified by an amount governed by the damping of the acoustic mode when the loudspeaker is tuned to the cavity resonance. Under this condition, the surrounding walls of the frame will vibrate in# sympathy or in resonance, so transferring the noise from the enclosed loudspeaker to the outside air. By ensuring a coincidence of air and structural resonance by careful design and tuning, a very efficient transfer of energy into acoustic energy can be achieved by the structure.

Although an aluminium extrusion is particularly well suited as the enclosing structure due to its inherent, low structural damping, other structural materials, such as steel or plastic, will also provide acceptable performance.

Referring now to Figure 2a, there is shown a plunger actuated switch 5 mounted in a door or window frame 6 with a plunger 7 of the switch 5 abutting the wall or sub-frame 8. The switch 5 has two spaced contacts 9 bridged by a T-piece 10 of the plunger 7 and the contacts 9 are connected by wires to the electrical circuit 2, shown in Figure 1. In the condition shown in Figure 2a, the electrical circuit 2 is unenergised. However, in the position shown in Figure 2b with the door or window open, the plunger 7 withdraws the T-piece 10 from one of the contacts 9 thereby energising the electrical circuit 2.

In Figures 3a and 3b there is shown a magnetic reed switch 13 mounted in the door or window frame 6 with a magnet 14 located in the wall or sub-frame 8. The magnetic reed switch 13 has contacts 9 which are bridged by a switch bridging element 15 and upon opening of the door or window frame, as shown in Figure 3b, so the switch is opened and the electrical circuit 2 energised. Alternatively, with the magnetic reed switch, shown in Figures 3a and 3b, it is possible to arrange the operation of the magnetic reed switch so that the electrical circuit 2 is energised when the switch contacts are both bridged by bridging element 15 so that instead of the switch being normally closed it can be revised to operate in the normally open condition.

The vibration switch 20, shown in Figures 4a and 4b, is mounted on a glass portion of the door or window and has a first contact 22 connected to a pivoting electrical member 23 having its remote end mounted within the confines of the ends of a norseshoe-shaped contact 24. Thus, when the glass is in its normal state, the member 23 sits between the ends of the horseshoe contact 24 without touching the horseshoe contact 24. When the glass is vibrated or broken, the member 23 is moved such that it engages one of the ends of the horseshoe contact 24 and the electrical circuit 2 is, thus, energised.

The electrical circuit 2 is more particularly shown in Figure Sin which a magnetic reed switch 13 is indicated although this of course could be replaced by the alternatives of the plunger actuated switch or the vibration switch. The reed switch 13 is connected via a fifteen second delay circuit 30 to a latching and oscillator enable circuit 31 which is arranged to provide an output to an oscillator 32 which is arranged to drive the loudspeaker 3 (not shown in Figure 5). A keyboard of ten switches 33 each marked with differing indicia, for example numbers, is connected to a code identifier 34 which is in turn also connected to the latching and oscillator enable circuit 31. A light emitting diode (LED) 35 is connected to the code identifier 34 as a check upon the battery power supply which is housed within the code identifier 34.In operation of the circuit a personal code identification is pre-programmed into the code identifier 34 and unless the appropriate code is entered via the keyboard switches 33 into the code identifier 34 so the latching and oscillator enable circuit 31 will produce signals to drive the oscillator and output stage 32 so that an audible alarm is produced upon the switch 13 actuating to indicate an open door or window position. The delay circuit 30 is provided so that should the door or window be opened by an authorised person prior to that person inserting the correct identification code via the keyboard switches 33 so that person may have sufficient time to subsequently enter the correct code identification into the code identifier 34.

The electrical circuit 2 could be arranged so that the frequency of the noise emitted by the loudspeaker 3 is varied to increase or decrease the radiated noise so as to serve a dual purpose of audible alarm, or, for example, a chime.

It will be realised that the relative dispositions of the electrical circuit and loudspeaker can be varied within either the framework defining the door aperture or within the windowframe or door as required without departing from the basis of the present invention of utilising a door or window hollow structure to be used as a resonant element for amplifying the sound produced by a noise source and for protecting the noise source.

Instead of using a conventional battery power supply, since the system is used on an external door or window frame it is alternatively possible to utilise a solar cell in the power source for the electrical circuit 2.

Claims

1. An audio warning system for a door or window including trigger means arranged to provide an output signal when the door or window is elicitly opened, noise source means connected to the trigger means and arranged to be mounted in a hollow portion of the door or window, said noise source means comprising means for producing electrical signals to drive a sound producing means, wherein, in operation, the enclosing walls of the door or window are utilised as a resonant structure to amplify the sound produced by said sound producing means.

2. An audio warning system as claimed in claim 1 wherein the sound producing means is chosen from one of a loudspeaker, buzzer or an air horn.

3. An audio warning system as claimed in claim 1 or 2 wherein the means for producing electrical signals includes a latching and oscillator enable circuit connected to be energised by the trigger means and to provide an output to drive an oscillator which is arranged to drive the sound producing means.

4. An audio warning system as claimed in claim 3 wherein preferably a plurality of keyboard switches each marked with differing indicia are connected to an indicia code identifier which is in turn connected to the latching and oscillator enable circuit, whereby an identification code is pre-programmed into the code identifier and the latching and oscillator enable circuit is disabled upon the correct code being entered on the keyboard switches.

5. An audio warning system as claimed in claim 4 wherein conveniently a delay circuit is interposed between the trigger means and the latching and oscillator enable circuit.

6. An audio warning system as claimed in any preceding claim wherein the trigger means is a plunger actuated switch, or a magnetic reed switch, or a vibration switch, in each alternative, said switch is operable to actuate the noise source means.

7. An audio warning system including a hollow framework of a door or window, trigger means arranged to provide an output signal when the door or window is elicitly opened, noise source means connected to the trigger means and arranged to be mounted in the hollow portion of the door or window, said noise source means comprising means for producing electrical signals to drive a sound producing means, wherein, in operation, the enclosing walls of the door or window are utilised as a resonant structure to amplify the sound produced by said sound producing means.

8. An audio warning system as claimed in claim 7 wherein the noise source means is mounted in the outer frame of the door or window defining the door or window aperture.

9. An audio warning system substantially as herein described with reference to, and as shown in, Figures 1, 2a, 2b, 5 or Figures 1, 3a, 3b, 5 or Figures 1, 4a,4b,5.