SE505825C2 - Mobile phone alarms with low power consumption - Google Patents

Abstract

A mobile telephone warning device has a battery-operated (3) detector circuit of low current consumption which is comprised of a transistor switch (2-8, C1, C2, R1, R2, R3, D) that is operative in detecting radio frequency signals captured via an antenna (1). The transistor is connected regeneratively via a low-pass filter (5, 7, C1, C2, R1, R2, D), which enables the transistor to self-adjust its operating point and therewith obtain optimal sensitivity.

Description

505 825 z be networked, and this limits their use. Purpose- The object of the invention is therefore to provide an easily movable mobile phone alarms that are battery powered but still have long maintenance intervals.

The inventive mobile telephone alarm is set forth in the appendix claim 1.

Embodiments of the alarm are set forth in the appended dependent patent claims.

The warning according to the invention comprises an antenna, and a battery-powered detector circuit that detects the presence via the antenna of an active mobile phone through a radio frequency output signal from the same, the detector circuit having an output whose output signal is arranged to trigger an alarm when one of the antenna captured output of mobile telephone radio frequency exceeds one set lower limit value. According to the invention, the at the detector circuit a transistor connection which is arranged to detect radio frequency signals and which is feedback via a low-pass filter to adjust its working point itself whereby the transistor connection has optimal sensitivity.

Because the detector / transistor connection is always optimal sensitivity, while power consumption is minimized. You can that is to say that the detector by automatic amplification trolls get a low power consumption so that a battery supply of the warning becomes possible, even then long battery replacement periods required or desirable.

The mobile phone alarm will be described in the following in conclusion to an exemplary embodiment shown in the drawing. 3 5Û5 825 Fig. 1 schematically shows a detector circuit belonging to one mobile phone alarm.

Fig. 1 shows a circuit comprising two parallel line branches 7, 8 which are connected to each other at points 2 and 6. At point 6, an output signal, marked Out, can be output. The circuit is supplied at point 6 from a power source 3 (battery) via a resistor R3. In line 7 there is a coil 5, a first capacitor C1, a voltage divider formed by resistors R1, R2, a second capacitor C2, and a diode D. The second lead 8 contains a transistor 4. An antenna 1 connects to the point 2.

The detector circuit shown in Fig. 1 consists of a transistor connection with low power consumption. The coupling detects radio frequent signals via the antenna 1, and includes a feedback low pass filter (5, 7, C1, C2, R1, R2, D) which allows tower 4 to adjust its working point itself. In this way one is achieved optimal sensitivity. When the circuit is energized with a battery package 3, capacitors C1, C2 will be charged. Cl then gets a voltage of about 0.65 volts at which the same voltage will be lie over base 41 to emitter 42 in transistor 4. The voltage over C2 is determined (set with) by the divider R1 / R2. The excitement over R3, the difference between the supply voltage and the voltage the voltage across C2 minus the forward voltage across D. This is then obtained power consumption over R3. In this stable position is the detector sensitive to AC voltage input to the base of transistor 4.

The AC voltage causes an increased power consumption through transistor 4 so that the voltage drops at the output to ground.

The output signal Out controls an alarm 9 which can be, for example acoustically or optically.

Claims (2)

505 825 4 P a t e n t k r a v A mobile telephone alarm comprising an antenna (1) and a battery-powered (3) detector circuit (1-8, R1, R2, R3, C1, C2, D), which senses via the antenna (1) the output signal of active mobile telephones of radio frequency, the detector circuit having an output whose output signal (Out) is arranged to trigger an alarm when an output signal of the mobile telephone frequency picked up by the antenna (1) exceeds a set lower limit value, characterized in that the detector circuit comprises a transistor connection which is fed back via a low-pass filter (2-8, C1, C2, D, R1, R2, R3) to adjust their operating point themselves. Mobile telephone alarm according to claim 1, characterized in that the detector circuit contains two parallel wiring branches (7,8), one connection point (2) of the wiring branches CL 8) being connected to the antenna HJ, while the other connection point (6) of the wiring branches C7,8) is connected to a power supply battery (3) via a resistor (R3), wherein the detector output signal can be taken out at the second connection point (6) between the branches (7, 8), that one line branch (7) from the first connection point (2) contains a coil (5), is connected to ground via a capacitor (C1), contains a voltage divider (R1 / R2), is connected to ground via a capacitor (C2), and contains a conductor leading to the first point (2) diode (D), while the second line branch (8) contains a transistor (4) whose emitter (42) is connected to ground, whose base (41) is connected to the first point (2), and whose collector (43) is connected to the second connection point (6).