How to check the hotel camera?

The hotel checks the camera as follows:

Turn on the camera function of the mobile phone, turn off the lights in the room and close the curtains. Leave the room in a dark state without any light. The darker the room, the better the inspection status! Then turn on the camera function of the mobile phone and walk around the room to see the dead angle and ceiling of the room. Television, air conditioning and other places where pinhole cameras may be installed. If there is a pinhole camera, you will see a red dot on your mobile phone. The red dot is a camera.

Any camera needs to collect visible light to image, so you can find the camera according to the light reflected by the lens. Shine a flashlight at each pinhole that looks like a hidden camera, and then observe the reflected light. The best way is to shine a flashlight on the front camera of a laptop or mobile phone and shake it back and forth. If you see this little color reflection, shake the flashlight and you will start.

Basic information of the camera:

The camera has an image sensor (CCD or CMOS). Generally, the sensor needs a crystal oscillator to generate a clock, which scans and images pixel by pixel (field clock) and line by line (line clock). The generators of these clocks will leak electromagnetic waves with a relatively fixed frequency.

Generally, the line clock is 12MHz to 30MHz, and the field clock is 15.625kHz(PAL) and 15.750kHz(NTSC). The former can be detected by multi-band radio in short wave band. If there is no camera with electromagnetic shielding, you can hear the clock signal about half a meter.