JPS622838Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a device for detecting a transmitter included in a wireless eavesdropping device or the like. Conventionally, there have been three types of detection devices of this type: (b) An antenna, a detection circuit, a DC amplifier circuit, a meter, or an alarm circuit. (B) An antenna, a wideband tuning circuit, a frequency band switching circuit, an amplifier circuit, a detection circuit, a DC amplifier circuit, a meter, or an alarm. (c) A full-wave receiver made up of circuits. However, in (b), even if the radio waves emitted by the transmitter are caught, it is impossible to distinguish whether the radio waves are coming from a wiretapping device or from a broadcasting station, etc. There are many detection errors,
It had the disadvantage of poor sensitivity, making it impossible to detect outdoors. (B) is more sensitive than (B), but has the drawback of causing detection errors similar to (B) when radio waves from a wiretapping device and a broadcasting station are present within the same broadband tuning range. (C) has extremely good sensitivity compared to (A) and (B), but
Since the frequency of the radio waves emitted by the eavesdropping device is unknown, it is necessary to repeat tuning by slowly turning the tuning dial and switching the reception band many times.Not only does it take time to tune, but the frequency ranges from several megahertz to several megahertz. A disadvantage is that receivers capable of continuous reception up to 100 megahertz are extremely expensive. Therefore, the present invention aims to eliminate the above-mentioned drawbacks, and by using sound waves of a specific frequency, it is possible to easily distinguish between radio waves from broadcasting stations and radio waves from eavesdropping devices, and also to make it possible to easily distinguish between radio waves from broadcasting stations, etc. and eavesdropping devices. By using a tuned superheterodyne receiver, the sensitivity equivalent to (c) above can be obtained, and there is no need for band switching for tuning, and the local oscillation frequency can be changed from a low frequency to twice or more high. It is unique in that it can continuously catch radio waves from eavesdropping devices over an extremely wide range by simply changing the frequency, and does not cause detection errors. Hereinafter, the present invention will be specifically explained using the drawings. The present invention consists of a specific frequency oscillation section and a reception section, the block diagrams of which are shown in FIGS. 1 and 2. In FIG. 1, 1 is an oscillation circuit for a specific frequency (including an appropriate amplification circuit), and 2 is an electroacoustic transducer such as a speaker. The specific frequency may be an audible frequency. When a sound wave with a specific frequency is emitted from a specific frequency oscillator as shown in Figure 1, if a wireless eavesdropping device is present, the microphone will catch the sound wave and modulate it, and the transmitter will output a high-frequency modulated signal. fire. However, the frequency of that output is unknown, and we will now call it _T. In Fig. 2, 3 is an antenna, 4 is a local oscillation circuit, 5 is a mixing circuit, 6 is an intermediate frequency amplification circuit (including a detection circuit), 7 and 11 are filter circuits for specific frequencies, and 8 is a low frequency amplification circuit. , 9 and 10 are display circuits, 12 is an amplifier circuit, and 13 is an alarm circuit. That is, in the receiver of the present invention, the mixing circuit 5 is not provided with a tuning circuit like a normal receiver. Then, the oscillation frequency ₀ of the local oscillation circuit 4 is made variable, and the relationship _H ≧2 _L is established between the lowest oscillation frequency _L and the highest oscillation frequency _H. For example, if ₀ is set to 13MC to 30MC and the oscillation output contains harmonics of many integer multiples in addition to the fundamental wave, the local oscillation circuit 4 It is possible to continuously and simultaneously oscillate an infinitely high frequency higher than the lowest oscillation frequency _L. Note that it is extremely easy to make the oscillation output of an oscillator contain many harmonics, and since the oscillation output of a normal oscillator contains many harmonics, no special measures are required. By the way, the tuning frequency of the intermediate frequency amplifier circuit 6 is
_i , then n ₀ - m _T = _i or m _T - n ₀ = _i between local oscillation frequency ₀ and transmitter output frequency _T.
When the relationship m=1, 2, 3,...; n=1, 2, 3,... holds true, _T is converted to _i and amplified by the intermediate frequency amplification circuit 6. amplified
_i is detected by a detection circuit included in the intermediate frequency amplification circuit 6 and amplified by the low frequency amplification circuit 8. Since the signal to be amplified here includes a low frequency signal from a broadcasting station in addition to a signal of a specific frequency, only the specific frequency component is extracted through a specific frequency filter circuit and further amplified. In the illustrated example, specific frequency filter circuits are provided in two stages, with the filter 7 at the front stage being an LC resonant circuit, and the filter 11 at the rear stage being a mechanical filter circuit. and,
The output of each filter circuit is amplified and displayed by display circuits 9 and 10 such as meters or LED (light emitting diode) analog indicators, and furthermore, an alarm circuit 13 generates an alarm sound. Next, an example of a method for confirming the presence of a wiretapping device from the specific frequency signal component detected in this manner will be described. The output of the LC resonant circuit 7, that is, the display value X of the display circuit 9 and the mechanical
The output through the filter circuit 11, that is, the display value Y of the display circuit 10 is compared, and the following judgment can be made based on the magnitude relationship.

[Table] Yes.
, the existence of a wiretapping device can be confirmed, but to investigate more accurately,
If Y or X becomes zero when you turn off the power to the device shown in Figure), it is certain. In addition, in order to confirm the installation location of the eavesdropping device, if you sound the alarm in the above or above conditions, lower the volume of the specific frequency oscillator, and search the room,
An alarm goes off in a certain space, confirming that there is a wiretapping device in that space. Naturally, this type of detection device must be portable due to its intended use, and the present invention can be easily configured to be portable. FIG. 3 shows an example of the present invention housed in a carrying case. In the figure, parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals, and their explanation will be omitted. FIG. 3A is a top view of the case with the lid opened, and FIG. 3B is a side view thereof. In the figure, 1' is the power switch of specific frequency oscillator 1, 1'' is the volume adjuster of 1, 4' is the main tuner of local oscillator 4, 4'' is the fine tuner of 4, and 15 is the receiver's. Sensitivity adjuster, 16
17 is a battery, 17 is a power switch, 18 is a lock, 19 is a case, and 20 is a handle. As explained above, the present invention provides a transmitter detection device that has a simple and inexpensive configuration, can easily distinguish between radio waves from broadcasting stations, etc. and radio waves from eavesdropping equipment, is easy to operate, and has high sensitivity without detection errors. Obtainable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a specific frequency oscillation device of the present invention, and FIG. 2 is a block diagram showing a receiving device of the present invention.
FIG. 3 is a diagram showing an example of the present invention housed in a carrying case. 1...Specific frequency oscillation circuit, 2...Electroacoustic transducer, 4...Local oscillation circuit, 5...Mixing circuit,
7, 11...Specific frequency filter circuit.

Claims (1)

[Scope of utility model registration request] It consists of an oscillator that emits sound waves of a specific frequency, and a superheterodyne receiver that does not have a tuning circuit in the antenna circuit or high-frequency circuit and has a local oscillation circuit that contains many harmonics in the oscillation output, and the above-mentioned The receiving device has a very wide reception band by simply changing the local oscillation frequency within a narrow range using harmonics of the local oscillation output, and has a filter circuit tuned to the specific frequency, so that the sound waves are A transmitter detection device such as a portable wireless eavesdropping device, characterized in that it detects a signal component of the specific frequency inputted via a transmitter such as a wireless eavesdropping device.