IE86000B1 - Staged detection and control of radio frequency emissions - Google Patents

Abstract

ABSTRACT A remedial device for association with apparatus that emits RF transmissions potentially harmful to humans or animal life, the remedial device including sensor means for sensing the generation of transmissions generated by said apparatus, detecting means for confirming the presence of transmissions, and remedial signal generation means, said detecting means being coupled to activate said remedial signal generation means, wherein said detecting means is arranged to detect transmissions emitted as a series of pulses, occurring at a frequency which may have a potentially harmful effect on humans or animal life, and said detecting means comprises a detection stage including a first integration means for integrated a sensed feeding the sensed transmission signal to a second integration means for integrating the sensed transmission signal over said predetermined time interval, and means for comparing the integrated values from said first and second integration means in a threshold or comparison means in order to determine whether said transmission have a significant time duration.

Description

STAGED DETECTlON AND CONTROL OF RADIO FREQUENCY EMISSIONS The present invention relates to methods and apparatus for protecting living systems from potentially adverse effects upon them of electric fields, magnetic fields and electromagnetic fields.

There are conflicting views as to the effects of electric fields, magnetic fields and electromagnetic fields on living systems. However there is considerable evidence that certain fields may be damaging to living systems including humans. It may also be that the detrimental effects are long term and their full impact has not yet been realised.

There has been a dramatic increase around the world in the use of electrically operated devices. All such devices have associated with them electromagnetic field emissions which, to varying degrees, have the potential to affect human health. Of particular interest are devices that transmit radio frequency (RF) signals and are used in close proximity to the human body, for instance cellular phones and other personal communication devices. At issue is the possibility that the safety standards under which these devices are manufactured which establish RF exposure limits to the users of these devices may not adequately account for effects below the thermal threshold, that is, at exposure levels well below levels that can produce measureable heating and can be attributed to direct energy transfer. The potential for such low level effects is supported by substantial evidence from epidemiologic studies and laboratory research which suggests that any measures that could minimize the effects of such exposure would be beneficial to the users of these devices United States Patent 5544665 is concerned with the protection of living systems from the harmful effects of electromagnetic fields and states that certain fields have an effect on the enzyme ornithine decarboxylase. The patent states that the potentially damaging effect can be reduced or eliminated if the detrimental electromagnetic field is altered either by switching the-field on and off or superimposing an electromagnetic noise field upon it. The patent further states that the effect can only be reduced if such alteration causes relevant characteristic properties of the field to change in time at intervals of less than 5 seconds and preferably at intervals from 0.1 to 1 second.

The characteristic properties that can be changed are said to be frequency, phase. direction, waveform or amplitude. Similar effects are discussed in Bioelectromagnetics 14 395 — 403 (1993) and Bioelectromagnetics 18 388 - 395 (1997).

United States patent 5544665 further describes various applications of the bio- The EMX Corporation has promoted batteries for cellular telephones that make use of the technology described in United States patent 5544665. When used with a cellular phone, these batteries produce a noise electromagnetic field that is superimposed over the local RF field thereby causing the total field to be irregular and thus not likely protection scheme including applications to cellular telephones. to cause biological effects. The noise was generated by a coil forming part of the battery pack. Activation of the noise was accomplished by monitoring the flow of electric current from the battery to the phone and using this as an indirect means to determine when the phone was transmitting in talk mode. This activation technique worked reasonably well with older phones but proved to be unreliable with newer phones which have applications, such as games and other entertainment applications that demand power from the battery and can cause false triggering of the noise and potentially unacceptable reduction in battery life.

The present invention overcomes these problems.

The present invention therefore provides a remedial device for association with apparatus that emits RF transmissions potentially harmfui to humans or animal life, the remedial device including sensor means for sensing the generation of transmissions generated by said apparatus, detecting means for confirming the generation of said transmissions, and remedial signal generation means, said detecting means being coupled for actuation of said remedial signal generation means, wherein said detecting means is arranged to detect transmissions emitted as a series of pulses, occurring at a frequency which may have a potentially harmful effect on humans or animal life, and said detecting means comprises a detection stage including a first integration means for integrating a sensed transmission signal over a predetermined time interval, a time delay means for feeding the sensed transmission signal to a second integration means for integrating the sensed transmission signal over said predetermined time interval, and means for comparing the integrated values from said first and second integration means in a threshold or comparison means in order to determine whether said transmissions have a significant time duration.

PATBI1 115 lE The invention may be associated with apparatus that includes most electronic devices that operate by transmitting RF signals which could be potentially harmful to human or animal life, but it is particularly useful with personal communication devices, such as cellular telephones, that are used in close proximity to the human body, and which transmit RF radiation.

Earlier studies have shown that RF radiation can cause potentially harmful effects if it is regular, meaning that it has constant properties, and is continuously applied for periods of over 10 seconds and that the potential harm can be substantially eliminated if the regularity period is reduced to no more than 1 second. The means to eliminate the potential harm in the present invention may superimpose a noise electromagnetic field on the potentially harmful radiation to produce a combined field that is irregular in time, meaning that it does not have constant properties in time, and therefore no longer has the potential to cause harm. Use of the noise field, which is hereinafter referred to as the remedial signal, is preferred as it allows for use of the electronic device without altering the manner in which it operates.

Said sensor means may be an RF sensor, for instance an antenna. which has been suitably configured to detect the particular radiation which is emitted by the electronic device and which is considered to be potentially harmful. Such sensor as preferred comprises an antenna which is responsive to a carrier wave frequency of the cellular handset that is a microwave frequency in the region of 0.8 to 2 GHz, as detailed below. As an alternative to a separate antenna, the coil for establishing the remedial field may be configured to detect RF transmissions. The advantage of this is the loss of the antenna component, but the accompanying disadvantage is the need to configure the coil for two-way operation, for example with a duplexing system. Whilst other methods of sensing the generation of RF transmissions might in theory be employed, for example sensing large current fluctuations in the apparatus, they would require some disturbance or modification of the apparatus. This would create further difficulty, particularly with cellular phone handsets. Further cellular phone handsets are of many different types, in particular with their antenna being in any part of the handset, or perhaps being constituted by the handset itself.

Said detection means for detecting the sensed radiation may comprise a passive detection stage, followed by an active detection stage. The passive detection stage is arranged to monitor RF emissions from the handset, and to rectify and integrate an RF detection signal. As preferred, one or more delayed versions of the sensed PATB|1‘l15 IE signal are compared with the current version, in order to determine whether there is RF radiation of significant duration, indicating that the handset is being used for speech transmission (talk mode). In this event, a power control signal is generated.

The passive detector stage does not require power for its operation, relying on the strength of the received signal, and therefore may be continuously operative, without any drain on the power source. In order to ensure that the sensed RF signal is of sufficient strength for detection, a coil, e.g. the coil for establishing the remedial field may in addition be configured to sense the RF transmissions, and to provide an additional signal to the detection means, as described below. in order to make a more accurate detection, an active detection stage, employing components such as transistors which require power, may be employed. The active detection stage is activated in response to the generation of the power control signal by the passive detection stage and includes circuitry which requires a power source for operation. The use of active components allows for power amplification and more accurate sampling of the antenna signal. Circuit components in the active detector stage may be configured to perform a similar function as the passive detector stage, that is, to compare integrated and averaged versions of the antenna signal, with a threshold value. Additional signal processing may also be added as necessary to make a more accurate and reliable detection of the antenna signal, in order to determine whether speech transmission is occurring, The active detector stage makes an detection of the antenna signal on successive time intervals and generated a signal that can take on either of two states to indicate the presence or absence of a talk mode signal. The signal detection intervai of the active stage should be preferably 100 ms. The output of the active detector is therefore a pulse train that indicates the status of the antenna signal, that is, talk-mode/not talk-mode, during successive detection intervals. The output of the active detector is employed to activate a remedial signal generator via a remedial signal control module The power control signal of the passive detection stage is applied to power control means, and is arranged to switch on a power source for activation of the active detection stage, and said remedial signal generator means. The remedial control generator means may include a remedial signal control module, which provides a control signal to the power source, and a control signal to a remedial signai generator module, for generating the desired form of remedial signal. The remedial signal control module is responsive to an output from the RF detection stage, and preferably comprises a microcontroller for executing one or more algorithms for PATBI1 115 IE controlling the remedial signal generator module. As preferred, the control module waits for a period of about 1 second until it receives a continual output from the detection stages, and then requests the power unit to provide power to the generator module, so that the remedial signal is generated for a period of about 3 seconds.

The waiting period of about 1 second is significant in that it represents a minimum -period in which the presence of a speech transmission signal may trigger a response in living tissue. On the grounds of power conservation, any radiation generated by the handset for a period of less than this minimum period is regarded as not requiring remedial action. The period of 3 seconds is chosen on the grounds of convenience, since with a longer period, a remedial field may be generated when it is not required, and a shorter period may result in excessive switching operations within the circuitry.

At the end of the 3 second period, the control module is reset unless or until a continual signal is again present from the RF detection stages.

The remedial signal generator module may include a digital noise generator, for example as described in US Patent No. 5,544,665, which is coupled through digital to analog conversion means and filter means, for providing an analog form of the remedial signal, to a coil which provides a means for establishing the remedial field in the neighbourhood of the handset.

Brief Descrigtion of the Drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a schematic block diagram of the remedial device according to the invention; Figure 2 is a more detailed block diagram of the passive RF detection stage of the embodiment of Figure 1; Figure 3 is a flow chart, illustrating the method of operation of the remedial signal generator and control module of Figure 1; Figure 4 is a schematic plan view and sectional view of a remedial device for fitting within a cellular phone handset; and Figure 5 is a plan view and sectional view of a remedial device, of credit card dimensions, for placing adjacent a cellular phone handset; and Figure 6 is a schematic block diagram, similar to Figure 1, of a modification of the embodiment of Figure 1.

PATBI11 15 IE Description of the embodiments All electromagnetic radiation consists of oscillating electric and magnetic fields and the frequency, which is the number of times per second at which the wave oscillates, determines their properties and the use that can be made of them. Frequencies are measured in hertz or Hz, where 1 Hz is one oscillation per second, 1 kHz a thousand, 1 MHz is a million, and GHz, is a thousand million. Frequencies between 30 KHz and 300 GHz are widely used for telecommunications, including broadcast radio and television, and comprise the radio frequency band.

Cellular mobile services operate at frequencies authorised by governments and typically operate within the frequency ranges 872 — 960 MHz, - 1875 MHz and 1920 — 2170 MHz. microwave frequency band which encompasses the range between 300 MHz and These frequencies are within the GHz. Other applications within this range include radar, telecommunication links, satellite communications, weather observation and medical diathermy. Although this invention may be used with waves of any frequency that are potentially harmful to humans and animal life, it is particularly useful with devices that operate on frequencies used for cellular telephones.

A radio frequency wave used to carry information in radio communications is referred to as a carrier wave. The radio frequency carrier wave of any system is produced by the transmitter as a sine wave, or other regular waveform. A carrier wave conveys no information if its properties do not vary in time. If the carrier wave is to convey any information, for instance, speech, music or digitized data, this information has to be added to it in some way. The process of varying one or more properties of a carrier signal with respect to the information that it is to carry is known as modulation.

Properties of the carrier wave that may be varied through modulation include for instance, amplitude, frequency, phase or a combination of these. For example, for AM (amplitude modulation) transmission, the electrical signal from a microphone produced by speech or music is used to vary the amplitude of the carrier wave, so that at any instant the size or amplitude of the RF carrier wave is made proportional to the size of the electrical modulating signal. In FM (frequency modulation), the instantaneous frequency of the carrier deviates from the carrier frequency by an amount dependent on the strength of the modulating signal. Phase modulation (PM) is a form of modulation that represents information as variations in the instantaneous PATBl1115lE phase of a carrier wave. FM and PM are very commonly used for current day radio communications.

A mobile phone (cell phone) sends and receives information (voice messages, text messages, emails, fax, computer data, downloads information etc) by radio communication. Radio frequency signals are transmitted from the phone to the nearest base station and incoming signals (carrying the information from the source to which the phone user is listening) are sent from the base station to the phone at a slightly different frequency. Base stations link mobile phones to the rest of the mobile and fixed phone network. Once the signal reaches a base station it can be transmitted to the main telephone network, usually by an optical fiber network.

Each base station provides radio coverage to a geographical area known as a cell.

Base stations (B8) are connected to one another by a mobile services switching centre (MSC), which tracks calls and transfer them as the caller moves from one cell to the next. An ideal network may be envisaged as consisting of a mesh of hexagonal cells, each with a base station at its centre. The cells overlap at the edges to ensure the mobile phone users always remain within range of the base station. Without sufficient base stations in the right locations, mobile phones will not work. if a person with a mobile phone starts to move out of one cell into another, the controlling network hands over communications to the adjacent base station.

The radiation with which this invention is particularly concerned is that emitted by the cellular telephone when it is transmitting or receiving information and particularly when it is transmitting information and in particular when it is transmitting speech as that is generally the time when it is in closest proximity to the head, and transmission radiation occurs for a significant length of time. in operation therefore the cellular telephone will be activated for use and will immediately generate the potentially harmful radiation at the particular predetermined frequency. The presence of the radiation will immediately be sensed by the sensor and detection means of the invention, which will then activate the remedial signal (noise) generator means that converts the constant potentially harmful radiation to a random benign wave pattern. The sensor and detection means also detects when the potentially harmful radiation is no longer being generated and deactivates the remedial signal until the next time that it is required. The choice of the frequency of the remedial signal will depend upon the nature of the electrical device and the PATBH115 IE frequency of the potentially harmful waves it generates. However we have found that for negating the potentially harmful effect of the radiation generated by use of the cellular telephone a remedial signal having a frequency in the range 30 Hz to 90 Hz is particularly useful.

An important aspect of an embodiment is that the radiation sensor and detector and the generator of the remedial signal can be incorporated into the cellular telephone without the need to alterthe structure of the ceilular telephone itself. We have found that this can be accomplished by the use of a miniaturised printed circuit containing the sensor and the detector and the remedial signal generator incorporated with the battery for the telephone. The invention may be used with any of the battery cells used for cellular telephones such as lithium ion batteries but use with the softer batteries such as lithium polymer batteries may be advantageous since the where the printed circuit board containing the components of this invention and the coil can be pressed into the battery casing to provide a battery with minimal reduction in battery capacity relative to a standard equivalent battery.

Referring to Figure 4. a schematic view is shown of such a remedial device, comprising a coil 2 for positioning on pressed into the surface of a handset battery 3, coupled to a unitary component 4, which incorporates the RF sensing antenna, and the electronics of the remedial device. The unit 4 may be coupled to the handset battery for power; alternatively it may incorporate its own power source.

An alternative embodiment of the remedial device is shown in Figure 5, in the form of an article resembling a credit card, and adapted to be positioned adjacent the cell phone, for example by placing the article in a holder or jacket for the cell phone. The article comprises a plastic substrate 5, with a coil 6 disposed around the periphery of the substrate, and incorporating a unitary component 7 which contains the electronics of the device and an antenna for sensing RF transmissions. A small battery 8 provides a source of power.

Although the invention is applicable to any cellular phone, use with cellular phones that employ the GSM protocol are particularly beneficial. This is the case because RF signais whose amplitude oscillates regularly with oscillation frequencies in the extremely low frequency (ELF) have been shown to be more likely to induce a measureable bioiogical response than unmodulated RF signals. GSM signals are transmitted as pulse bursts with pulse width of 0.577 ms and pulse repetition rate of PATBH115 IE .615 ms, or equivalently, frequency of 217 Hz. Therefore these signals are likely to cause biological effects. CDMA signals may or may not be transmitted using a GSM- like regular pattern; therefore, while biological effects cannot be entirely disregarded, they are likely to be less pronounced than those resulting from exposure to GSM RF signals.

This embodiment discloses a device that generates an ELF noise magnetic field when a cellular telephone is transmitting RF signals while operating in talk mode. it is distinct from prior art in that it senses the presence of the talk mode RF signals by a non—contact means that does not require interfacing directly with the phone. It is also distinct from prior art in that it includes means for activation of the remedial signal that incorporates specific features that account for certain response characteristics of biological cells to EMF stimuli. In the typical application the device described in this embodiment is located in close proximity to the phone. for instance within the battery pack that provides power to the phone. The device operates continuously with very low power consumption which increases when the remedial signal needs to turned Figure 1 shows a general block diagram representation of the principal components of this preferred embodiment. Four principal modules are identified in this figure: RF Signal Detection Module 20, Power Control Module 22, a source of Power 24.

Remedial Signal Control Module 26, and Remedial Signal Generator Module 28. .

The RF Signal Detection Module 20 includes an Antenna 30, which is coupled directly to a Passive RF Detector 32, and coupled directly an Active RF Detector 34.

The Antenna may be tuned to operate at any of the common cellular phone frequencies including, for instance, 890-960, 1710-1880 MHz (GSM/DCS), and 825- 894, 1820-1990 MHz (CDMA/PCS), or may be a wide band antenna that can operate within the cellular frequency range (~800 to 2000 MHz). It may be implemented as a commercial off-the-shelf chip antenna such as the MD1506, or a custom-made PCB antenna. The Passive RF Detector 32 serves the function of continuously monitoring the RF emissions from the phone and providing a control signal to actuate other components that consume more power. It is further represented in Figure 2. In the preferred embodiment the Passive RF Detector requires no external power, relying on the strength of the received signal from antenna 20, and additionally a signal 86 from a coil 84, as will be described. With reference to Figure 2, the Passive RF Detector Front End 36 may be implemented using either a single or dual diode PATBl1‘l 15 EE detector. The dual diode detector configuration which provides full wave rectification is preferred as it can also be used to provide power for the other components of the passive RF detector. This approach is often employed to actuate passive RFID devices. For instance, the HSMS-2822 or HSMS-286C Schottky diode pairs connected in series may be used for this purpose. The passive RF detector should preferably be configured to detect only talk mode RF signals. However, it may also detect RF signals transmitted in standby mode. Therefore, a comparison on successive measurements is necessary to ensure that a talk mode signal has been detected. This may be implemented, for instance, by sampling the RF front end output three times such that each sample is delayed from the next by a delay time t and then comparing the three samples. If the three samples come within a set threshold of each other, the RF signal is determined to be a likely talk mode signal.

Sampling should be accomplished by integrating the signal over a time interval Ti, preferably between 50 ms and 100 ms, with successive samples delayed by the same time Ti. This is implemented as shown in Figure 2 by first and second delay elements 38, 40, and first, second and third integrator sample and hold circuits 42, 44, and 46, which are coupled to a comparator or thresholding unit 48. Circuit 42 is coupled directly to the front end 36, circuit 44 is coupled to front end 36 via first delay unit 38, and circuit 46 is coupled to front end 36 via first delay unit 38 and second delay unit 40. Unit 48 of the passive RF signal detector produces one of the three ON/OFF control signals (All ONIOFF Control P) for the power control moduie, to switch on the power unit 24.

Power unit 24 provides power via power control module 22 to Active RF detector 34.

The Active RF Detector 34 is powered up when a talk mode signal is detected. This detector is intended to make Detector 34 is coupled directly to antenna 30. more accurate and stable measurements of the talk mode signal. It may be implemented using commercial off-the-shelf components. As with the Passive RF Detector, sampling should be accomplished by integrating the signal over a time interval Tia, preferably of the order of 50 ms. Two successive measurements should be averaged and compared against a fixed threshold value to generate an ON or OFF signal. The output of the Active RF Detector is a train of ON/OFF values that are updated in successive 100 ms intervals. The functionality of the Active RF Detector may also be implemented using the passive RF detector. However this option would require carefui adjustment to minimize false positive talk mode detection. The output of Active RF Detector 34 is applied to remedial signal control module 26. Module PATBl1‘l15lE receives power via power control module 22 from power source 24 in response to the control signal from passive RF detector 32.

The Power Control Module 22 includes three power controls signals, one from the Passive RF Detector for all active components (All ON/OFF Control P) 50, and two from the Remedial Signal Control Module 26, one for the Active RF Detector 34 (Active ON/OFF Control) 52 and one for all active components (All ON/OFF Control A) 54. Signals 52, 54 are applied through an OR gate 56 to power source 24, so that if either of the signals for all active components is ON, the power control module 22 provides a signal to actuate all components that are powered by a power source.

The Remedial Signal Control Module 26 provides an enabling/disabling signal (Active ON/OFF Control) 52 via a disabling circuit 58 for reduced power consumption of the Active RF Detector 34 as described below. In the preferred embodiment the power source is the cell phone battery cell but another power source, for instance, an auxiliary battery, could also be used.

The Remedial Signal Control Module 26 incorporates the rules to control the activation of the remedial signal based on the input from the RF Detection Module . This module may be implemented in hardware but is most easily implemented in software using, for instance, a microcontroller. Figure 3 shows a block diagram of a flow chart of operation for the Remedial Signal Control Module. The Acquire and Compare block 60 synchronizes with the output of the RF Detection Module and reads the values of successive samples spaced at 100 ms intervals. Reading is carried out over a time interval greater than 1 s, but preferably of the order of 1 s. if all the values are ON as at 62, a signai is applied to the remedial signal generator module 28 so that the remedial signal is turned ON, as at 64, 66 for a time interval Tp, preferably of the order of 3 s. A shorter time (>100 ms) would require more frequent detection of the RF signal. A longer time may increase the power consumption to an unacceptable level. For the first 2 s (or Tp-1 s for Tp>1 s) that the remedial signal is ON, the power control signal for the active RF detector is set to OFF to reduce power consumption (Active ONIOFF Control OFF). At the end of this 2 second interval as at 68, 70, 72, the Acquire and Compare block is Reset and the check cycle to determine whether the status of remedial signal is repeated. if any of the values measured in the compare and control block is OFF, the power control signal for all active components is set to OFF (All ON/OFF Control Off) as at 74, 76 and the device reverts to monitoring the RF signal from the phone in passive mode.

PATBI1115 lE The Remedial Signal Generator Module 28 may be implemented as electromagnetic noise using an analog circuit or a mixed analog/digital circuit as previously described in United States Patent 5544665 and related patents. For the purpose of this application, the preferred embodiment would employ a mixed analogldigital approach using a microcontroller for the digital section. This is advantageous because a preferred embodiment of the remedial signal control module also uses a microcontroller that could be employed to accomplish both functions. In a preferred embodiment the digital noise generator 80 can be implemented as a pseudo random noise generator consisting of appropriately interconnected shift register sequence to which an input clock signal is applied. The output bits and clock frequency are then selected to achievethe desired sequence repetition rate. For instance, with a clock rate of 4 KHz and an 18 stage shift register sequence, a repetition period of about 1 minute can be obtained. Using a digital to analog converter (DAC) and an appropriately selected band pass filter 82 a suitable noise signai can be obtained.

For instance a 3-bit DAC and a 30-90 Hz band pass filter produce a noise remedial signal that satisfies the specifications of United States Patent 5544665. An audio signal amplifier of standard design and a coil 84 of suitable dimensions can be used to complete the remedial signal generator. in a preferred embodiment, the coil should be a multi-turn coil with more than 100 "turns and having resistance of less than 30 Ohms. For instance, AWG 36 or AWG37 copper wire can used to satisfy the coil resistance and number of turns requirements. in this embodiment, the coil 84 is configured to sense the RF transmissions from the handset, and to provide a signal on line 86 to passive RF detector 32, in order to amplify the strength of the sensed signal input to detector 32. Such an arrangement requires that the sensed transmissions signal and the remedial noise signal can be effectively isolated. To avoid such isolation requirements, a modification of the embodiment of Figure ‘I is shown in Figure 6.

In Figure 6, similar parts to those of Figure 1 are denoted by the same reference numeral. An additional coil 90, termed a wake-up antenna, comprises a physical coil of wire or a coil traced on the PCB of the electronics of the embodiment. The effect of coil 90 is to amplify the strength of the sensed signal input to detector 32.

Claims (1)

1. CLAIMS .A remedial device for association with apparatus that emits RF transmissions potentially harmful to humans or animal life, the remedial device including sensor means for sensing the generation of transmissions generated by said apparatus, detecting means for confirming the generation of said transmissions, and remedial signal generation means, said detecting means being coupled for actuation of said remedial signal generation means, wherein said detecting means is arranged to detect transmissions emitted as a series of pulses, occurring at a frequency which may have a potentially harmful effect on humans or animal life, and said detecting means comprises a detection stage including a first integration means for integrating a sensed transmission signal over a predetermined time interval, a time delay means for feeding the sensed transmission signal to a second integration means for integrating the sensed transmission signal over said predetermined time interval, and means for comparing the integrated values from said first and second integration means in a threshold or comparison means in order to determine whether said transmissions have a significant time duration. A remedial device according to claim 1, wherein said apparatus comprises a personal communications device that emits RF transmissions in use. A remedial device according to claim 2, wherein said personal communications device comprises a cellular telecommunications handset. A remedial device according to claim 3, wherein the remediat device is located within said cellular telecommunications handset. A remedial device according to any preceding claim, wherein said sensor means comprises an antenna responsive to transmissions emitted by said apparatus. A remedial device according to any preceding claim, wherein said sensor means comprises or includes a coil which is configured to sense said transmissions. A remedial device according to any preceding claim, wherein said detection stage comprise a passive detection stage, having a front end which rectifies the sensed transmission signal in order to derive power for operation, and which is arranged continuously to monitor said transmissions. A remedial device according to claim 7, wherein said passive detection stage, in response to a positive determination that said transmissions have a significant time duration, is arranged to initiate a power on signal for switching power on in an active detection stage of the detecting means, wherein the active detection stage is coupled to receive the sensed transmission signal, and includes a first integration means for integrating a sensed transmission signal over a predetermined time interval, a time delay means for feeding the sensed transmission signal to a second integration means for integrating the sensed transmission signal over said predetermined time interval, and means for comparing the integrated values from said first and second integration means in a threshold or comparison means in order to determine whether said transmissions have a significant time duration, and to activate, in response to a positive determination, said remedial signal generation means. A remedial device according to any preceding claim, wherein a said detection stage has a second time delay means coupled to the first time delay means for feeding the sensed transmission signal to a third integration means for integrating the sensed transmission signal over said predetermined time interval, and arranged for comparing the integrated values from said first, second and third integration means in said threshold or comparison means. A remedial device according to any preceding claim, wherein said significant time duration is about 100 milliseconds. A remedial device according to any preceding claim, wherein said remedial signal generation means includes a remedial signal control means responsive to said detecting means, a remedial signal generator, and means for establishing a remedial field in the vicinity of the apparatus, wherein the remedial signal control means is arranged to monitor an output from the detecting means for a first predetermined time period sufficiently long to indicate that radiation from the handset may be potentially harmful, following which the remedial control means is arranged to initiate the supply of power to the remedial signal generator to establish a remedial field for a second predetermined time period. A remedial device according to claim 11, wherein the remedial signal control means, once activated, is arranged to disable, at least partly, the detection means to reduce power drain. A remedial device according to claim 11 or 12, wherein at the end of the first predetermined time period’, the remedial signal control means is arranged to be reset, and to await further outputs from the detection means. A remedial device according to any of claims 11 to 13, including a power control means for controlling a source of power, and wherein said detecting means is arranged to provide an enabling signal to the power control means for supply of power to said remedial signal generation means. A remedial device according to claim 14, wherein the remedial signal control means is arranged to provide an enabling signal to the power control means for supply of power to said remedial signal generator A remedial device according to of claims 11 to 15, wherein said remedial signal generator comprises a digital noise generator, which is coupled through digital to analog conversion means and filter means, for providing an analog form of the remedial signal. _ A remedial device according to any of claims 11 to 16, wherein said remedial control means and/ or said remedial signal generator comprises a microcontroller encoded with algorithms to perform selected digital functions of said remedial control means and/or said remedial signal generator. A A remedial device according to any preceding claim, wherein said means for establishing a remedial field in the vicinity of the apparatus includes a coil for establishing a remedial electromagnetic field.