Method and device for disabling cellular phones

METHOD AND DEVICE FOR DISABLING CELLULAR PHONES

0002The present invention relates to a method and also to a device for disabling the use of cellular phones within a predetermined confined area. Cellular phones, which have come into wide spread use, frequently

0003produce disturbances to those in the immediate vicinity. The use of cellular phones can even introduce a hazard, such as when used in the vicinity of electronic instrumentation at airports, hospitals, and the like. Many locations

0004therefore request that cellular phones not be used, or expressly ban their use.

0005Such a ban requires the user to turn-off his/her phone when entering such an

0006area, but users frequently neglect to do this. As a result, cellular phones

0007frequently create undesirable disturbances and even health hazards.

0008An object of the present invention is to provide a method, and also a device, for disabling the use of cellular phones within specified confined areas without depending on the user to turn-off the cellular phone.

0009According to one aspect of the present invention, there is provided a method for disabling the use of a cellular phone within a confined area in a cell

0010site, comprising transmitting within the confined area a jamming signal continuously varying in frequency to cover the service band for the respective

0011cell site and of a power level to have a range sufficiently only for the respective

0012confined area.

0013The service band refers to a specific band of frequencies used by the

0014cellular telephone system to locate a subscriber found in the cell site by sending its address. The service band can appear as any band in the cellular system. Sometimes on a separate channel and sometimes in a receptions channel. It is

0015jointly used by all the cell sites in the network to inform a subscriber which speech channel is to receive the call. The subscriber also uses the service band frequencies to indicate the ready status of the phone to receive a call, and to indicate the power of the signal in the respective cell site.

0016A number of important advantages are provided by jamming the service

0017frequency bands rather than the complete transmission band. Thus, since the power required for this purpose varies with the band width of the transmitted

0018signal, less power is needed to disable the cellular phones within a pre-determined confined area. This enables the disabling to be better restricted

0019to a specific confined area and without disturbing adjacent areas not intended to

0020be affected. In addition, the disabling will be effected only before a telephone

0021connection has been made in the restricted area, and will not interfere with telephone conversations that have already started to take place before the blocking device has been activated (in most cases). Accordingly, there will be

0022less chance that the device will interfere with transient persons traveling through

0023the restricted area.

0024According to further features in the described preferred embodiment the

0025frequency of the jamming signal is continuously varied in specific frequencies

0026from about 800 MHz to about 980 MHz. This frequency range of the jamming or disabling signal is presently the one used by cellular phone networks but this could change in the future. In addition, the power level of the jamming signal is from 0.5 to 10 milliwatts, preferably about 1.0 milliwatt. This value could also change in the future.

0027According to another aspect of the present invention, there is provided a

0028device for disabling the use of a cellular phone within a confined area in a cell

0029site, comprising a small portable housing including a voltage controlled oscillator controlled to vary the frequency of a jamming signal; a low frequency oscillator

0030controlling the voltage controlled oscillator to control the frequency repetition rate of the jamming signal; a power amplifier receiving the output of the voltage

0031controlled oscillator and amplifying the output to said power level of about 0.5 to

003210 milliwatts; and an antenna receiving the output of the power amplifier and

0033transmitting the output to the respective confined area.

0034As will be described more particularly below, the foregoing method and device may be used for automatically disabling cellular phones within a confined

0035area, such as a meeting room, hall, vehicle, airport, hospital, etc., where their use may create undesirable disturbances or even dangerous hazards. The disabling of the cellular phones is effected automatically and does not require any particular act by the carrier of the cellular phone.

0036Further features and advantages of the present invention will be apparent

0037from the description below.

0038The invention is herein described by way of example only, with reference

0039to the accompanying drawings, wherein: Fig. 1 schematically illustrates a cellular phone and a device constructed in accordance with the present invention for disabling the use of such a cellular phone within a confined area; and

0040Fig. 2 is a block diagram illustrating the electrical circuitry in one form of disabling device constructed in accordance with the present invention.

0041The cellular phone 2 illustrated in Fig. 1 is of a commonly-used type. It includes a small portable housing 3 having an ear piece 4 disposed in

0042the upper end of the housing, a mouthpiece 5 pivotally mounted to the lower

0043end of the housing, a keyboard 6 containing depressable number and control

0044keys, a display 7, and an antenna 8. At the present time, such cellular phones generally operate in the frequency band of 800-960 MHz, but future networks

0045will probably work at higher frequencies, in the GHz spectrum. The broadcast band and the receiver band constitute most of the 800-960 MHz band width, with the service band being about 870-960 MHz. For example, one system operates at 870-890 MHz, and another at 920-960 MHz. Such cellular telephones generally transmit at power levels of about 600-700 milliwatts.

0046Since such cellular phones are well known, further details of their

0047construction and operation are not set forth herein.

0048In accordance with the present invention, a device, generally designated 10 in Fig. 1, is provided for disabling the use of a cellular phone within a

0049confined area, such as a room, hall, vehicle or the like. For this purpose, the

0050portable disabling device 10 is physically placed in the confined area to be neutralized. It continuously transmits a jamming signal continuously varying in frequency to cover the service band spectrum for the respective cellular sites, and of a power level to have a range sufficiently only for covering the respective confined area.

0051In the embodiment described herein, the frequency of the jamming signal is continuously varied in specific frequencies from about 800 to 980 MHz so as to cover the service band or the respective cell site. By thus covering the

0052complete service band all the cellular phones within that confined area will be

0053disabled since they will not have a service band available to them, and therefore will display a no service available message in display 7.

0054In the embodiment of the invention described below, the power level of

0055the jamming signal is preferably about 0.5 to 10 milliwatts. This is usually

0056sufficient to jam the confined area but not to disturb the use of cellular telephones outside the confined area. Preferably the power level of the jamming or disabling signal is about 1.0 milliwatts. This power level which is two or three orders of magnitude below the 600-700 milliwatts transmitted by the cellular telephones, would normally not require FCC approval nor is it likely to

0057produce hazards to instrumentations or controls that might be caused by the 600-700 milliwatt power level transmitted by cellular telephones.

0058The disabling device 10 illustrated in Fig. 1 includes a housing 11 which

0059encloses the electrical circuitry described below illustrated in Fig. 2. The

0060illustrated device includes an on/off switch 12, an LED indicator 13 indicating when the unit is operating, a manual range setting control 14 for setting the range of the device, a sweep frequency control 15 permitting manual setting of the lower frequency and the upper frequency of the jamming signal, and a manual control 16 for presetting the sweep frequency repetition rate of the jamming signal.

0061Unit 10 illustrated in Fig. 1 further includes a display 17 for displaying the

0062signal strength of the cellular telephone system signal received in the respective area of the cell site. The power level of such a signal depends on the location of the confined area to be neutralized, and also the prevailing weather

0063conditions. It determines the range setting 14, which setting controls the power

0064of the jamming signal to assure that it is sufficient for disabling only the cellular phones in the respective confined area where the unit 10 is located.

0065As shown in Fig. 2, the electronic circuitry within housing 11 of the

0066disabling unit 10 includes a voltage controlled oscillator 20 which generates the jamming signal at a frequency controlled by a low frequency oscillator 21 , and a power amplifier 22 which amplifies the jamming signal and transmits it into the

0067confined area via antenna 18. The frequency of the jamming signal generated by the voltage controlled oscillator 20 is preset by the manual frequency setting 15, and the sweep frequency repetition rate is controlled by the low frequency

0068oscillator 21 as preset by the sweep rate setting 16. The output power or range

0069of the transmitter jamming signal may be preset by manual control 14; alternatively, it may be automatically controlled by the signal strength detector 23 which detects and measures the signal strength of the cellular telephone system at the respective confined area, displays it in display 17, and automatically controls the power amplifier 22 via the range setting circuit 24. Since the signal strength detector 23 cannot operate at the same time that the disabling unit 10 transmits the jamming signal, detector 23 may be in the form of a separate unit providing a reading of the detected signal strength, enabling the user to manually preset the power setting (24) of the disabling unit. Disabling unit 10 is preferably in the form of a small, portable,

0070self-contained unit. Accordingly, it includes its own battery power supply 25 for

0071supplying the power to the above-described circuit components via the on/off switch 12 and the LED indicator 13. It will be appreciated that the various controls illustrated in the unit of Fig. 1 are shown for purposes of example only, and that some of these controls could be

0072pre-set at the factory, could be omitted, and/or other controls could be included. Also, the disabling unit can be built in the form of a synthesized oscillator in which the frequencies are controlled by a crystal in a phased locket loop (PLL) system to prevent problems in manual adjustment of the frequency or in its stabilization with respect to time, temperature, different voltages, different

0073antenna loads, etc. Also, the system could use a programmable attenuator to

0074control the range instead of a programmed amplifier.

0075Therefore, while the invention has been described with respect to one preferred embodiment, it will be appreciated that this is set forth merely for purposes of example, and that many other variations, modifications and

0076applications of the invention may be made.