GB2185141A - Communication and/or warning system - Google Patents

Abstract

A system for providing a subject with information independently of any visual or audible signal or transmission includes a vibratory transducer 15, the subject being operatively in physical touch therewith or with a body or element acted on by the transducer, the transducer responding to signal data, for example derived from a sensing transducer 12 to provide the subject with information on an analogue basis. Many applications are disclosed. Fig. 1 shows a breathing system with a pressure sensitive transducer 12 which acts through a central circuit 13 to activate a vibratory transducer 15 as a danger warning. Fig. 9 shows a toy with tactile heartbeat effect activated by a switch 62. <IMAGE>

Description

SPECIFICATION Communication and/or warning system This invention relates to communication and/or warning systems particularly but not exclusively for communicating with orwarning subjectswho are permanently ortemporarily deprived offull use of one or more of the normal faculties of sensory per ception whetherdueto some inherent mental or physical handicap or disability or due to their i n- volvement in a situation in which the environment and/or their activities preclude or substantial Iy ob- struct some means of communication, e.g. visual and/oraudibleorwhich make such demands on their faculties that some means of communication may be dangerously or undesireably distracting and/or may go unnoticed.Subjects so handicapped and/or in this kind of situation are hereinafter referred to as "deprived subjects".

Examples of deprived subjects with which the invention is particularly but not exclusively, concerned are where the subject is operating in a hazardous or hostile environment using such protective means as breathing or other life support systems, e.g.when carrying out underwater work using a diving chamber, pressurised or other suit, and/or breathing mask or like equipment; or when using protective helmets, masks and/or suits for rescue or other em ergencywork in environments affected byfire, smoke, toxic gases, radiation or the like e.g. in fire or mine rescue services; or when the subject is an aeronautorastronautwho not only has to wearpres- surised suits or other similar life support systems but who is also carrying out operations requiring extreme skill, care and concentration where visual or audible distraction may in itself be hazardous. Even if the subject is not confined by protective means the circumstances of the environment may preclude normal communication e.g. due to darkness and/or ambient noise level; or the extreme concentration of the subject on the task in hand may cause him or her to ignore or not notice conventional signals e.g. on dials or other indicators even where these showthat danger levels have been reached orcontinueto be exceeded.

The invention also has application in assisting the physically or mentally handicapped, forexample paralysis making conventional communication difficultor impossible, or patients having to be treated in artificial environments to isolate or protect them from infection or assist or substitute fortheir natural functions e.g. breathing, or possibly during temporary disablement e.g. under certain conditions of anaesthesia. Another application is in providing a soothing, reassuring or comforting signal e.g. to a child.

Another application, as described in greaterdetail in the end partofthe description and defined in claim 20 ofthe appended claims, provides a toy, doll or other article with a tactile heart beat effect to give a soothing, reassuring or comforting signal to a child or other subject and/orto provide a plaything which more closely simulates a living body.

Another application ofthe invention isto provide secure communication with a subject, even ifthey are in the close vicinity ofthe subject and/or to provide a security signal orwarning e.g.thatan object has been tampered with in a unauthorised manner.

It is known to provide aids to communication, particularly for use by the disabled, using a tactile signal output, for example an alarm system providing a vibratory signal which can be felt by the subject but these arrangements are limited in operation, usually the only information passed to the subject is that a certain condition has or has not taken place, e.g. a door bell ortelephone has been rung or an alarm clockorfire alarm has gone off, i.e. the transmission to the subject is on a digital basis limited to "on" or "off" and transmission of more detailed information or data can only be made with difficulty and, more importantly, taking up considerable time using some kind of digital code which can only be perceived and understood slowly by the subject.

The object of the invention is to provide a simple and effective means of communication with deprived or other subjects which is speedy, secure, and effective, readily provided e.g. in combination with protective clothing or like equipment, and reliable and durable in operation.

According to one aspect ofthe invention there is provided a communication system for transmitting information to a subject without the use of signals visible to or audible by the subjector others includ- ing receiving means into which signal data is input from an external source, and transducing means converting output from the receiving means into a form capable of being sensed by the subject other than audiblyorvisually.

Preferably at least part ofthe converted output provides information adapted to be sensed by the subject on an analogue basis.

The transducing means may include one or more vibratory transducers in operative contact with an area or respective areas ofthe user's bodyfortactile sensing thereby. Said areas may be related to a spatial content of the signals, for example areas of the left and right and/or upper and lower limbs may be used to sense signals which are a function of direction or orientation.

The signal data may be transmitted from a remote station e.g. bya radio ortelephone link (which may also be used for conventional audio communication with the subject or others where and when circumstances are appropriate) and/or it may be generated automatically by sensor means to provide information to the subject of conditions in his or her immediate or a remotelocality,forexampleformoni- toring safety levels or detecting and providing feed-back on obstacles or hazardous conditions in or nearthe subject's immediate environment.

According to a further aspect ofthe invention a system for communicating the occurrence of a variation in fluid pressure includes a pressuretransducerhaving aflexiblediaphragm arranged to be deflected in response to a change in pressure differential acting on its opposing faces, an electrically conductive region of or on the diaphragm coacting with a plurality of electrical contacts to actuate an electrical circuit ofwhich the contacts form part in use on deflection ofthe diaphragm.

Preferably the diaphragm is a thin membrane of an elastomeric material, e.g. natural latex, which will respondto very low pressure differentials, the electrically conductive region being a lightweight plate of or coated with a noble metal oran alloythereofe.g.

silver, bonded to a central area of the membrane.

Preferably there are three contacts, also of or plated with silver or other noble metal, in a plane parallel to the general plane of the conductive region to ensure positive and even contact loading. The circuit may be arranged to respond if any one ofthethree points of contact is broken, e.g. where the transducer is used to monitor loss of positive pressure.

It is also preferred that the circuit incorporates a high input impedence switching device, e.g. operating at an input impedence of about 5 kilo-ohmsto ensure response at the lowcontact pressure available from the transducer (which can be adapted to respond to pressure differentials as low as 1 mm water gauge) through the impedence should not be so high as to be adversely affected by e.g. excess humidity causing a water droplet to bridge the gap between the plate and contacts.

Some practical examples ofthe application ofthe invention in its various aspects are now more part icularlydescribed with reference to the accompanying drawings.

In a first example ofthe invention shown diagrammaticaily infigure 1, a positive pressure breathing system e.g. for use in mine rescue or other hazardous conditions where the ambient atmosphere is unsafe to breathe due to the presence of toxic gases and/or dust contamination, smoke, lack of oxygen or the like includes a breathing mask or helmet 10fed with air or other breathing gases from a backpack 11 e.g. in a closed circuit positive pressure breathing system of known kind.

A pressure transducer 12 (described infurtherde- tail hereafter) is located atsomeconvenientposition in the helmet or breathing system to monitor any dangerous pressure drop therein, i.e. to ensurethata predetermined positive pressure differential between the interior and exterior ofthe helmet or mask is maintained at all times.

If there is loss of pressure for any reason thetransducer 12 acts through a control circuit 13 to activate a vibratory transducer 15 in contact with a part ofthe user's body, in this example shown as built in to the wrist band of a protective suit 16 ofwhich helmet 10 forms part.

Thearrangementensuresthatthe userwill become immediately aware of any failure of pressure in the breathing system even if he is concentrating on the task in hand and even if his faculties ofsightand hearing are occupied. The vibration on the wrist etc cannot be missed and the user can then take immediate steps to rectify the defects or withdraw from the dangerous situation before suffering any harm.

As a further precaution the signal from the pressure transducer may also be transmitted to a remotesta- tion, e.g. using a radio or other communication system, so that supervisory or backup personnel are aware of the failure and can arrangeforspeedy rescue if the subject himself does not correct the fault or withdraw.

The operation of the preferred form of pressure transducer will now be described in greater detail with reference to Figures 2-5; Figure2being a block diagram, Figure3being asectionalviewofthetransducer and switch unit, Figures4a, b, cbeing details of its diaphragm and contacts, and FigureS being a circuit diagram.

The transducer and its associated switching is provided as a single unit enclosed in a box30.

Thetransducerassembly itself is located in a cylindrical housing 31 extending through a wall of the box its outer end being ported to atmosphere byway of a dustfilter and its inner end within the box being acted on by the positive pressure, in this example of the breathing helmetthough it will be appreciated that the unit can readily be connected for other pressure monitoring applications.

Housing 31 contains a flexible diaphragm 32 in the form of a natural latex membrance 32 (Figure 4) hav ing its borders clamped between open centered backing and compression pieces 33,34. Membrane 32 is 0.127mm thick and has hard a silverdisc34 0.0762mm thick and 7.62mm in diameter bonded to its centre preferably using an acrylic adhesive (for example Dunlop reference SAS 300) giving a strong bond without becoming brittle so that it does not readily fracture under repeated switching action.

The free area of membrane 32 is 50.8mm in diame terandanairtightseal between the rear face of the membrane and backing piece 33 and between the latterand thewalls ofthe housing is assured by means of adhesive or other sealing means.

Asupport bar36 mounted on the outerfaceof compression piece 34 extends across the aperture in the latter and carries a group of three silverplated contacts 37 arranged in a triangle formation, their tips extending through bar 36 in a plane parallel to membrane 32 in its undeformed condition and in close proximity to plate 35.

With the innerface of membrane 32 subjected to even slightly greaterfluid pressure than its outer face it will be deflected outwardly so that plate 35 abuts the three contacts 37. Use of three contacts gives a flat "seating" to the disc in this condition and positive electrical bridging between all three. Use of one ortwo contacts onlywould allow plate 35 to rock with consequent excess distortion of the membrane, while use of four or more contacts would resultin unreliable abutment between the plate and one or more of them.

Arechargeable power cell 40 housed within box 30 operates a high input impedence switching circuit 41 now described with reference to Figure 5. The input impedence ofthis circuit is about 5 kilo-ohms so asto be operational with the very low contact pressure available between plate 35 and contacts 37. This impedence level is not high enough to be adversely affected by high humidity, e.g. if a water droplet bridges the plate and one or more of the contacts when they were otherwise separated.In this application the transducer is being used to monitor any failure in positive pressure in the mask and the arrangement is "fail safe" in that the circuit is activated in a "stand by" condition but held inoperative as long as all three contacts 37 are effectively bridged by plate 35 but if contact of any one or more of them with the plate is broken the circuit responds by providing a warning signal. A comparator l.C.I. activates a switching transistor T.R.I. on any break of contact, the emitterfrom the latter operating the indicator, e.g. the tactile transducer previously referred to (not shown in Figure 5) and/or some other indication such as an LED and/ortransmission of a signal to a remote station. Diode gates DG enable a common socket connection 45 to be used both for output e.g.

to the tactile transducer and electrical inputfor recharging power source 40 when the unit is being serviced.

The transducer uses CMOS circuitry so that in the standby condition (i.e. with the diaphragm pressurised and the contacts closed) current consumption is minimal,typically70-80 microamps.

Tests have shown that the unit is highly sensitive and responsive, it will respond to pressure differentials as little as 1 mm water gauge and gives ex tremely fast response due to the verythin material used for membrane 32 and the very lightweightof the disc35. Tests have also shown that the response ofthe device is substantially unaffected by extremes oftemperature other adverse operating conditions and the effect of gravity on the diaphragm is again minimal so that the unit will operate reliably and con- sistently in any orientation.The latex material of the membrane is not subjected to any high stress and will perform reliably long term without being affected by fatigue or corrosion e.g. the work hardening which may result from many cycies of operation where metal diaphragms are used.

To prevent excessive distortion of the membrane where high pressure differentials are applied it may be located between rigid limiting plates which are slightly concave so as to permit its operational deflection these plates being apertured to allow the membrane to sense the pressure changes.

In use a test check will be made before the breathing helmet is put into service, i.e. while the latter is at atmospheric pressure, underthis condition there is no pressure differential across the diaphragm, the contacts will be open and the tactile transducer or other indication should operate. If this is not the case or if, when the helmut is pressurised, the indicator does not change state a faul condition is indicated.

The check is also "fail safe" in that if the diaphragm is damaged or its airtight sealing is not maintained, or if the bonding of disc 35 to it should fail in service and unsafe condition will be indicated.

The above pressure transducer has numerous applications, for example it can be used to monitor the breathing cycle of a subject, either with feedback to the subject him or herselfand/orto an automatic recording device or visual or audio read-out such as a cathode ray tube, audio tone generator or the like e.g. for medical use in monitoring the condition of a patient and/or the operation of anaesthetic or life support systems; or where the subject is working in an artificial environment and/or under hazardous conditions, for example firemen, mine rescue workers, divers, aeronauts or astronauts, orworkers in toxic or contaminated atmospheres eg chemical workers, workers handling asbestos etc.

Feedback to the subject him or herself may be val uableforexample in the case of young children hav ing respiratory or nerve defects making them liable to "cotdeath" or breathing failurewhen asleep; breathing would be automatically monitored and a tactile transducer used to wake the child or other subject at a predetermined low threshold danger level.

The pressure transducer may also be used in var ious ways where pressure differentials orthe abs- ence of any pressure differential is to be monitored, particularly where the pressure differences are small and sensitive and speed response is wanted. The op eration of a cooling or otherfan can readily be moni tored by using the transducer in the input or output duct, the read-out can readily be provided at a re mote station; and the device may have applications in other kinds of pneumatic or hydraulic apparatus, for example for data transfer. A reliable check can be maintained on anypressurised compartment e.g. in aircraft or underwater vessels with earlywarning of even slight changes from normal pressure.

The pressure transducer may take the form of a pneumatic switch for an operatorto hold or depress, giving a "dead man" alarm and possibly switching off or rendering safe apparatus in his charge if the switch is released.

The device can also be applied as a movementdet vector as it is much more sensitive than mechanical/ electrical microswitches, inertia switches and the like. For example if the pressure transducer is con nected to a sealed flexible bag any physical move mentthereof e.g. by picking it up, will cause suf- ficient change of pressure differential to triggerthe device and provide a signal. This may have security applications e.g. to warn of any attempt to remove or tamperwith valuables or, in warfare, it could be used for anti-personnel mines or bombs. Such a bag or enclosure may have medical applications, for example in detecting or analysing muscle movement in limbs, the limb being enclosed in a sleeve or bag and the pressure changes in the latter being monitored.

In another form of movement detection the device can be used to indicate the fall or other sudden displacement or the halting of movement of an object or structure, the diaphragm being subjected to pressure differential due to the velocity of air striking it.

The device may also have application in thevolumetric analysis of gases and in pneumatic systems for counting, detecting passage of articles orthe like, an airjet being directed across a gap to impinge on the diaphragm, any break in the jet e.g. by an intervening object, triggering the circuit. This arrangement may be useful where optical or ultrasonic devices are impractical e.g. in dirty or dusty environments.

Arrangements incorporating the vibratory trans- ducerfortactile sensing having further applications whether or not used in combination with the pressure sensing transducer referred above. Aswell as providing simple digital response at a given threshold level derived from an external sensor, for examplethe pressure transducer or other device; a variable signal, e.g. by changing frequency pulse width or amplitude modulation, may be provided which is a function of a value derived from the sensor etc., i.e. providing analogue information transfer and/or pulse coded information transfer.

For example coded information could betransmit- ted through atactile transducer using a) constant rhythm patterns, or b) bit coded patterns.

In case (a) it has been proved that it is not difficult for an average person to decode up to five different rhythm patterns can be achieved using changes of frequency and/or change of pulse width or duty cycle.

In case (b) pulse character patterns can be trans mitted based on a variety of bit codes, for example 1-4 pulses followed by an absence of pulses for a constant period (this allows the subject an expectant period when his senses are mentally ready to accept the next information) and numbered pulse information of this type can be used to transmitthe status of a number of sensors successively or can be used in a scan facility using the numbering system as an identifying code or even a time period indicator.

The volume of information transmitted which can readily be understood bythe subjectwithoutambi- guity can be increased by using more than one tactile transducer, each associated with a respective part of the body. This can give a spatial element e.g. by indicating left and right hand orientation using the left and right limbs and/or attitude or altitude using arms and legs. This latter method of communication,e.g.

in directing a vehicle, may have substantial advantages in that the subject's attention does not have to be focused on instruments such as a compass orturn indicator (e.g. when flying or driving blind) and it mayprovide much speedier response in that many subjects have difficulty in immediatelytranslating a verbal command (e.g. "turn left") into the necessary action and such commands may be mistransmitted or misunderstood in the heat ofthe moment.

Acombination of analogue and digital types of signal may be usefully confined. For example a pulsed tactile transducer can operate at a slow rate (e.g. 0.5hz.) which could be the starting rate at which a signal is initiated when an external sensor is activated at a predetermined threshold level, for example an emergency limit level. Subsequent changes in conditions read by the sensor could be transmitted by, for example, a change of pulse frequency, pulse width or amplitude ofthe tactile output. The pilot or driver of an aircraft, land vehicle or on or underwater vehicle could be made aware of an unsafe condition and could subsequentiy sense through his body im provements or deterioration of the condition e.g. in response to his corrective actions or lack of action.

Thus feedback can be provided of operating con ditionswhich might otherwise be very difficult for him to sense correctlyand/orwhich he would find unduly distracting to derive from such equipment as dials and indicators having to be referred to visually and possibly needing to be watched substantially continually.

Numerous types of information could be transmitted in this way, e.g. operating conditions of the vehicle itself - pressure, temperature, tension ete and/or the manner in which the vehicle is operating, for example an indication of altitude or, more importantly, ground clearance in an aircraft, a tactile signal being transmitted to the pilot which he will notice im- mediately and cannot readily ignore if, for example, he flies dangerously low or is approaching a mountainside or other obstruction. This type of arrangement may be particularly valuable in fighter aircraft or other combact vehicles when the pilot or other subject is fully occupied under high stress conditions with speedy reaction times being essential to his safety.Even in ordinary road vehicles a warning system incorporating the invention will be extremely valuable e.g. in indicating excess speed or in emergency conditions e.g. indicating wheel locking or wheel spin when braking or on slippery roads.

The tactile transducers can be strapped to the body or incorporated in close fitting articles of clothing, e.g. gloves, gauntlets or footwear, or even more con veniently, they can be built into the equipment, for exam ple in to seats, l eg or arm rests, floor pads or pedals, or handles, steering wheels or other controls.

Another application of the invention takes the form of a doll, soft toy, or other article having a tactile heartbeat effect. This is of use for soothing or comforting a child orothersubject in distress or liableto become distressed, for example a very young baby or possibly a mentally disturbed patient, and/or as a plaything giving a lifelike effect to an inanimate objectsuchasadoll ortoyanimal.Asthesubjectclasps the article closelyto him or her a pressure or other pickup transducer would sense th subject's heart beats and would transmit these tQa a tactile output transducer so that the heartvibrat)ons would be felt by the subject (a degree of audible transmission might also be included).It is well established that the regular heart beat e.g. ofthe mother is particularly comforting and reassuring e.g. to very young babies.

In anotherversion ofthe lattertype of article ortoy the heart beat effect is artificially generated and transmitted using a tactile output transducer. Automatic switch-on may be provided using a micro switch actuated when the doll or other article is clasped or held, e.g. when pressure is applied to the front of a doll and/or a touch-sensitive switch may be provided. Use ofthe pressure ortouch switch has the advantage that the transducerwill automatically switch off when the actuator is released by the sub- ject or when the subject's grip ortouch relaxes, e.g.

when a child has been soothed to sleep.

The heart beat effect may be closely simulated for tactile sensing by a device incorporating an electronic pulse generating circuit and a motor driven displaceable mass, the motor being driven intermittently in response to pre-selected characteristics ofthe generated pulses.

Conveniently the latter device is in the form of a compact lig ht-weig ht self-contained battery pow eredunitwhichcan readily be built into a "soothing" article such as a soft toy or possibly into an article of clothing ora pillow or cushion. A soft article is preferred as this will tend to muffle or damp superflous or unwanted responses of the transducer e.g. audible mechanical noise and/or minor out of phase transmissions having in mind that cost con siderations and the need for a compact reliable unit capable of volume production may preclude use of the most accurate and clear simulations which could otherwise be produced.

One example of the last mentioned type of device is now more particularly described with reference to Figures 6to 9 ofthe accompanying drawings wherein: Figure 6is a graphic representation of a human pulse or heat beat, Figure 7is a block diagram of this example ofthe device, Figures a diagram of an example of a control circuitforthe device, and Figure 9 is a diagrammatic sectional view of a soft toy incorporating the device.

Figure 6 is a graphic representation derived from experimental work on changes in electrical potential which gives a close representation of human cardiac action i.e. the pulse rate and the characteristics of each heart beat pulse in the form in which it is sensed bytouch. Itwill be seen, in particular, thatthe wave form of each pulse has a practically vertical full heightfrontorspike reducing almost in stantaneously to a lower level followed by a sloping and then much steeper drop back to rest with a gap before the next pulse. Thus a tactile simulation ofthe heart beat requires each pulse to commence with a sharp "kick" followed by preferably controlled dying away so that the pulse pattern resembles that shown in Figure 6 or, at least, lies fairly closely within the envelope of that pulse form.

In this example the device takes the form of a selfcontained unit 51 designed for economical volume production to be readily incorporated within an art icle such as a stuffed soft toy 50 as indicated in Figure 9.

Control means ofthe device incorporates an electronic pulse generator 52 driven from a battery or other power source 54 to provide signal data input in the form of pulses preferably at a frequency in the range of 60-80 Hz.

Transducing means in the form of a small rotary electric motor 56 is driven intermittently from the power source by way of a power switching reiay device 58 operating in response to the pulse inputfrom generator 52.

The shaft of motor 56 mounts an eccentric, i.e. out of balance, mass in the form of aflywheel-likedisc 60.

While it is contemplated that other forms and arrangements of displaceable masses, e.g. a weight guided for rectilinear movement, might be incorporated in the transducing means and be driven bya rotaryornon-rotarymotore.g.a linearmotororsol- end, the rotary mass is preferred because its response will be substantially unaffected by the orientation of the toy or other article incorporating the unit.

Whicheverway up the top is held disc 60 will swing until its heaviest portion is downwards when the motor is at rest.

The circuit is arranged so that the steep and sharp front of each pulse delivered from generator 52 provides sufficient starting torque to motor 56 to throw disc 58 very sharply from its position of rest, con venientlythrough not more than half a revolution throwing the unbalanced mass upwards. Preferably this rise time should be not more than 0.25 seconds.

It is also preferred that the driving current to the motor is switched off before it has completed the half revolution and it may be desirable to incorporate a shunt across the motor terminals to short therm as and when the power isturned off to prevent anyten dencytooverrun due two back EMF.

Various parameters may be selected or adjusted to give the most acceptable and effective tactile output as felt buy a child or other subject holding thetoyor other article closely. There will be some modification of the effect due to the stuffing and othersurrounding material ofthe soft toy. The mass and eccentricity of disc 60 can readily be changed; the starting torque or "kick" applied to the motorcan be varied in power and or duration; the amplitude ofthe pulse provided from generator 52 can be varied (provision forselective adjustment may be built into the circuit) and the overall shaping of the pulses may also be varied relativeto an optimum envelope e.g. as shown in Figure 6.

Although the soothing, comforting or pleasureable tactile effect of the heart beat as experienced bythe unborn child inthewomb is weli known the precise parameters required for this effect are ex tremely difficult to evaluate and have not, as yet, been positively established. It is possiblethatsome variation in characteristics may best suit different subjects, for example a very young child as distinct from a mentally disturbed adult.

Thus it may be desirable to include ready means for setting or adjusting one or more of the parameters e.g. frequency and/or amplitude.

In the example shown in Figure9the batteryor other power supply ofthe unit is controlled by a pressure switch 62 located at or near the front ofthe toy 50 so that the device is switched on when the toy is clasped or hugged but will switch off automatically when the pressure is relaxed.

Figure 8 is a diagram ofoneformofcircuitwhich could be used in the device though it isto be under stood that other forms ofcircuit e.g. of pulse gener- ator 52 could be employed.

Claims (29)

1. A system for providing a subject with information independently ofanyvisible or audible signal or transmission including transducing means operable to convert or apply signal data input received by and or generated in the system into a form capable of being sensed by feel with the subject in physical touch with thetransducting means or with a body or element acted on by said means in use.

2. A communication system fortransmitting information to a subject without the use of signals vis- ible to or audible by the subject or others including receiving means into which signal data is input from an external source, and transducing means converting output from the receiving means into a form capable of being sensed by the subject otherthan audiblyorvisually.

3. A system as in claim 2 wherein at least part of the converted output provides information adapted to be sensed by the subject on an analogue basis.

4. A system as in claim 2 or3 wherein the transmitting means includes one or more vibratorytransducers in operative contactwith an area or respective areas of the user's bodyfortactile sensing thereby.

5. A system as in claim 4wherein said areas are related to a spatial content of the signals, for example areas of the left and right and/or upper and lower limbs may be used to sense signals which are a function of direction or orientation.

6. A system as in any preceding claim including meansfor receiving signal datatransmittedfrom a remote station.

7. A system as in any preceding claim including sensor means for generating the signal data auto- maticallyto provide information to the subject of environmental conditions.

8. Means for communicating the occurrence of a variation in fluid pressure including a pressure transducer having a flexible diaphragm arranged to be deflected in response to a change in pressure differential acting on its opposing faces, an electrically conductive region of or on the diaphragm coacting with a plurality of electrical contacts to actuate an electrical circuit of which the contacts form part in use on deflection ofthe diaphragm.

9. Means as in claim 8 wherein the diaphragm is a thin membrane of an elastomeric material which will respond to very low pressure differentials,the electrically conductive region being a metal plate bonded to a central area of the membrane.

10. Means as in claim 9 wherein the elastomeric material is natural latex.

11. Means as in claim 8 or 9 wherein the plate is a lightweight plate of or coated with a noble metal or an alloy thereof.

12. Means as in any one of claims 8 to 11 wherein there are three contacts in a plane parallel to the general plane ofthe conductive region.

13. Means as in-claim 12whereinthecircuitis arranged to respond if any one of the three points of contact is broken.

14. Means as in any one of claims 8 to 13wherein the circuit incorporates a high input impedence switching device.

15. Means as in claim 14 wherein the switching device operates at an input impedence of about 5 kilo-ohms.

16. Meansforcommunicatingtheoccuranceofa variation in fluid pressure substantially as hereinbefore described with reference to and as shown in Figures 2-5 ofthe accompanying drawings.

17. A communication system as in any one of claims 8-16.

18. A positive pressure breathing system including a communication system as in anyone of claims 2to7or17.

19. A breathing system substantially as herein before described with reference to and as shown in Figures 1-5 of the accompanying drawings.

20. A system for providing a subject with information in the form of simulated heart beats giving a mentally soothing or pleasureable effectto be sensed by feel including control means for auto maticallygenerating or providing signal data input having characteristics of a natural rate of heart beat, and transducing means converting or applying said data input in the form of vibrations sensed by feel when the subject is in physical touch with the transducing means or a body or element acted on by the latter means in use, said vibrations having the tactile effect of heart beats.

21. A system as in claim 20 wherein the control means includes an electronic pulse generating circuit and the transducing means includes a motor driven displaceable mass, the motor being operatively driven intermittently in response to preselected characteristics ofthe generated pulses.

22. A system as in claim 21 wherein the motor is a rotary motor and the mass is an eccentric or out of balance mass rotated or angularly displaced by the motor.

23. A system as in claim 22 wherein each pulse from the generating circuit is applied to power the motor with rapid high starting torque sufficientto power the mass through movement of not more than one half revolution.

24. A system as in claim 23 wherein the duration of said application of power is not more than 0.25 seconds.

25. Asystem as in anyone ofciaims2l to24 wherein the generated pulses have a frequency in the range of 60 to 80Hz.

26. An article including a body or element incorporating a system as in any one of claims 20 to 25.

27. An article as in claim 26 including a pressure or touch sensitive switch for activating the system.

28. An article as in claim 26 or27 in the form of a soft toy.

29. A system for providing simulated heart beats to be sensed by touch substantially as hereinbefore described with reference to and as shown in Figures 6 to 9 of the accompanying drawings.