mini project on mobile detector

i have got a circuit for mobile detector and i am not sure how to increase the range of the detector. i shall post full details of the circuit and if any one can tell me how can i interept the signals through some noise or some other medium prompting the user to either switch of the phone or cut the call.....

if any body can tell me i would be really grateful

the details are as given below

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Parts: [/FONT][FONT="][/FONT]
[FONT="]R1____________100K 1/4W Resistor[/FONT]
[FONT="]R2______________3K9 1/4W Resistor[/FONT]
[FONT="]R3______________1M 1/4W Resistor[/FONT]
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[FONT="]C1,C2_________100nF 63V Polyester Capacitors[/FONT]
[FONT="]C3____________220µF 25V Electrolytic Capacitor[/FONT]
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[FONT="]D1______________LED Red 10mm. Ultra-bright (see Notes)[/FONT]
[FONT="]D2___________1N5819 40V 1A Schottky-barrier Diode (see Notes)[/FONT]
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[FONT="]Q1____________BC547 45V 100mA NPN Transistor[/FONT]
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[FONT="]IC1____________7555 or TS555CN CMos Timer IC[/FONT]
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[FONT="]L1_____________Sensor coil (see Notes)[/FONT]
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[FONT="]B1_____________1.5V Battery (AA or AAA cell etc.)[/FONT]
[FONT="]Device purpose:[/FONT][FONT="] [/FONT][FONT="][/FONT]
[FONT="]This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED.
The device must be placed a few centimeters from the cellular phone, so its sensor coil L1 can detect the field emitted by the phone receiver during an incoming call. [/FONT][FONT="][/FONT]
[FONT="]Circuit operation:[/FONT][FONT="] [/FONT][FONT="][/FONT]
[FONT="]The signal detected by the sensor coil is amplified by transistor Q1 and drives the monostable input pin of IC1. The IC's output voltage is doubled by C2 & D2 in order to drive the high-efficiency ultra-bright LED at a suitable peak-voltage. [/FONT][FONT="][/FONT]
[FONT="]Notes:[/FONT][FONT="] [/FONT][FONT="][/FONT]

• [FONT="]Stand-by current drawing is less than 200µA, therefore a power on/off switch is unnecessary. [/FONT][FONT="][/FONT]
• [FONT="]Sensitivity of this circuit depends on the sensor coil type. [/FONT][FONT="][/FONT]
• [FONT="]L1 can be made by winding 130 to 150 turns of 0.2 mm. enameled wire on a 5 cm. diameter former (e.g. a can). Remove the coil from the former and wind it with insulating tape, thus obtaining a stand-alone coil. [/FONT][FONT="][/FONT]
• [FONT="]A commercial 10mH miniature inductor, usually sold in the form of a tiny rectangular plastic box, can be used satisfactorily but with lower sensitivity. [/FONT][FONT="][/FONT]
• [FONT="]IC1 must be a CMos type: only these devices can safely operate at 1.5V supply or less. [/FONT][FONT="][/FONT]
• [FONT="]Any Schottky-barrier type diode can be used in place of the 1N5819: the BAT46 type is a very good choice.
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this is the link to the circuit

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this is another link to another circuit

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and any one sugeest me which is a better circuit