It’s unpleasant when they rang your doorbell and you don’t know at all who is on its side. You can call yourself as you like, introduce yourself - by anyone. Voice can be faked. Only with your own eyes having seen the otherworldly guest, you can open the door. In the Middle Ages, an observation slit, like a loophole, served for this. Today is the peephole. However, peephole peephole is great discord.
First of all, you should determine the viewing angle of the eye. If it is not enough, one of the attackers can simply crouch - and now he is not visible, and the second one rings the doorbell with a “trustworthy person” (two unfamiliar men at the door are always more suspicious than one).
Therefore, the optimal viewing angle of the door peephole starts at 180 degrees. Security experts advise choosing 200 degrees - due to the fact that at the edges of the view this angle gives less distortion. In this case, it will be possible to consider the entire visitor, up to shoes on his feet.
The material from which the door peephole is made is also of no small importance. Say goodbye to plastic immediately and forever: cheap but inefficient. Electrifying plastic, like a magnet, attracts dust to itself, moreover, over time, the optical properties of plastic slowly but inevitably deteriorate. Better to put it once, but "for centuries." Then pay attention to the union of metal and glass, optical or spectacle. Only metal should be coated so as not to darken over time.
Another important safety feature associated with the door peephole is the curtain that covers it from the inside. The fact is that the peephole itself can issue to the criminal whether the owners are at home or not, by changing the lighting in his lens. However, if you first bring your face closer to the eyepiece of the eye, and then open the shutter, for the outside lens the lens will remain dark. For effective operation, the curtain should tightly overlap the eyepiece hole, and when opening it should not make a single sound.
Of course, there can be no question of any noiselessness if the child remains at home. Indeed, in order to look through the peephole, he first needs to be brought into the hallway, and then climb on it. The problem is solved by a more complex, but also safe device such as a periscope. In this case, the eyepiece of the eye is located at the level of child growth.
The last of the considered optical options, the most suitable for both adults and children, is a panoramic door peephole. His eyepiece has been replaced with
frosted glass, onto which, like on a screen, the entire viewing area in front of the door is projected. The image on the screen is perfectly visible from 1.5-2 meters.
Around the middle of the 90s of the last century, electronic devices began to actively spread in Russia, which had previously been installed only at secure facilities. They made it unnecessary to enter the hallway at the
doorbell. In fact, if a digital camera looks through the peephole, just looking at the computer screen to which it is connected is enough. Or the camera can generally be positioned on the landing so as to survey it all (and more than one if desired). And if you add an
infrared lamp, then the twisted-off light bulb will not help criminals. The added microphones and speakers will allow negotiating with the visitor / s, without again leaving the computer, with which you can also conduct video recording just in case ...
At the same time, however, do not forget that the
stairwell is a common room, and it is forbidden to conduct covert shooting on it by law.