How to check whether there is a pinhole camera when staying in a hotel?

There are more and more candid photos now, which makes us hard to prevent. So how do you judge whether there is a pinhole camera in the room when you go out to stay in a hotel? Let's have a look.

First of all, let's talk about where the pinhole camera is most likely to be placed: 1, and the roof (with a good view). 2. Lamp holder, electric clock, air source panel, smoke detector, etc.

3. Electrical appliances hanging on the wall, such as wall clock, air conditioner, ventilator, etc.

Behind the loudspeaker network of TV and stereo.

5. Alarm clock and decorations on the bedside table.

6, the lower edge of the table and chair.

Turn on the camera function of the mobile phone, turn off the room light and close the curtains. Let the room have no light, and the darker the inspection conditions, the better! Then turn on the camera function of the mobile phone and walk around the room to see the dead corner of the room. Ceiling, TV, air conditioner and other places where pinhole cameras may be installed. If you see a red dot on your mobile phone, it is a camera.

All cameras need to absorb visible light into the image. All lenses can reflect light well. The reflected light is very distinctive. First, even if the environment is white, the reflected light will have color (different colors of glass have different refractive indexes). Second, the lens is a convex lens, and the reflection point is much smaller than the incident light. This may be an important means to find a camera. The way to find it is also very simple. Put a flashlight in front of each hole that looks like a hidden camera and observe the reflected light. The best way is to shake the flashlight back and forth on the front camera of your laptop or mobile phone. If you see a little color reflection and flashlight shaking, it is the reflection of the camera lens.

The camera has an image sensor (CCD/CMOS). Generally, a sensor needs a crystal oscillator to generate a clock (field clock) for scanning image pixels line by line. These clock generators may leak electromagnetic waves at a relatively fixed frequency. The line clock is generally 12 MHz to 30 MHz, and the field clock is generally 15.625 kHz (PAL) and 15.750 kHz (NTSC). The former can be detected by short-wave multi-band radio. If there is no electromagnetic shielding camera, you can hear the clock signal about half a meter.

Because devices with high internal power consumption such as image sensor /DSP/MCU will become hot, and because image processing consumes relatively computing resources, these devices will eventually come into contact with heat dissipation. But this detection requires a thermal imager.

The other is a communication socket. No one just puts a camera or collects videos. Therefore, the video must also be wired or wireless. The wireless output can be detected by a broadband RF scanner, for example, 50 MHz to 3GHz. Nine times out of ten, it is problematic for household appliances to emit radio in abnormal frequency bands. The outlet of the cable is generally distributed by power lines, and the line detector mentioned above is also applicable. Some cameras will use local memory cards, so there will be traces of frequent movement of people, and photographers will often appear, which is too risky. This method is rarely used.

Finally, the power supply. Because contact cameras need to work for a long time, they usually don't use batteries for power supply. So the power supply is the fox's tail and an essential camera. This limits the need to unplug the camera or install it in electrical appliances. The former can be found by wire/metal detectors suitable for general construction projects. The latter can help narrow the search scope and focus on electrical appliances.