Probably few people know that Alexander Graham bell the inventor of the well — known phone made another discovery, which was considered even more significant. We are talking about the electron-optical communication system, it is possible to wirelessly transmit voice at a distance using reflected solar beam. Compared to radiotelephony communication that consumes relatively much electric energy, the invention of hottelephone (so called the bell system) and was, in fact, a real technological miracle.
What effect such a device?
Remember all the famous Sunny Bunny. With the help of a mirror the beam is directed at a photodetector. Now we have to make sure that he carried the information we need. This flat mirror is fixed on the end face of a hollow cylinder, If someone talks into the cylinder under the action of sound, the mirror will begin to oscillate a beam of light is modulated by an audible frequency.
The task of receiver is to convert with a photocell light energy into electrical energy.
The first hottelephone, created by bell in 1880, could transfer voice to a distance of 215 m. and you Try to build a similar design, using the materials taken from foreign magazines.
The photo transmitter metal tube Ø 25,4 mm, length 56-60 mm.
In the end it has a mirror diameter of 25 mm smooth, thin aluminum foil, well reflecting the sun’s rays. It is fixed with adhesive on a nylon headband that increase the susceptibility of the mirror to sound.
A ray of light falls on a photocell connected to the low-frequency amplifier: this receiver (Fig. 2). And its sensitivity was high, used a parabolic mirror Ø 406 mm., Together with ULF, a small-sized dynamic head and the battery is installed in the housing of the plywood (Fig. 1).
Fig. 1. Design of a sensor:
1 — body, 2 — mirror, 3 — block, 4 — valve, 5 — door, 6 — adjusting strap, 7 — connector socket, 8 — stand.
Fig. 2. Schematic diagram of hottelephone.
Some body parts are connected to each other using wood glue and screws. To the base attach the wooden stand, and to top — carry handle. Inside the housing color black nitro, and the outside white. The black color will reduce accidental reflections, while white is visible in the distance.
A parabolic mirror attached to rear of housing, four strips of wood with strips of elastic foam. In addition, a piece of the same material with a size of 30X30 mm is glued in the center of the back wall. After the mirror is fixed, to the full completion of the work necessary to close a thick towel or blanket (to prevent damage).
Of course, not everyone can get a parabolic mirror of large dimensions. Not a problem, instead use aluminum drive where in winter the boys ride from the mountains. Clean the paint from the inner surface and carefully Polish it to a mirror Shine.
If your house has been preserved lens from televisions first releases, then it will replace the mirror. However, the design of the photodetector in this case you will need to change a little.
The photocell mounted on the end of a wooden rod (Fig. 3). At its opposite end is mounted a miniature telephone plug, through which the photocell is connected to the ULF.
Fig. 3. Device for installing photocell:
1 — male, 2 — core, 3 — cell, 4 — conductor, 5 — tape PHL.
The connector socket is located on the two-piece strap (see Fig. 1). Sections interconnected with hinges, can be folded when the receiver is not working.
The photocell should be installed in . the focus of the spherical mirror. To do this, in the strap, make two slits: a guide longitudinal centerline, and then level at the distance of 25, 57, 108, 191 mm from the end of the plank. Drilled holes Ø 4.8 mm, remove with a chisel the wood between the first-second and third-fourth holes. The lower sections attach a square wooden block, drill a hole and insert the connector socket. The bar and stem color black.
Now install the bar in the middle of the door. Insert the plug into the socket and aim at a spherical mirror, a strong beam of light. Moving the bar in a horizontal direction, make reflected from the mirror light focused on the photocell. Mark on the Palace centres of the slots of the strap and drill the holes.
The bar fasten with two screws and nuts.
On the inner side of the door, install the speaker and make the necessary electrical connections according to the diagram.
Then proceed to the establishment of the photodetector. Next to the transmitting mirror device select transistor radio by configuring it to any broadcasting station. Receiver hottelephone position at a distance of several meters from the transmitter so that it reflected from the light beam falling on the surface of the spherical mirror. Plug with photocell install into the slot on the bar and focus the light beam so that the signal was maximum. If you did everything correctly, you will hear the broadcast.
Now gradually move the sensor from the transmitter and check the quality of reception at intervals of 15-30 m until then, until the signal becomes very weak. Don’t forget that the Earth’s rotation causes a deviation of a sunbeam from the original set position. So from time to time need to adjust the position of the beam between the transmitter and the receiver hottelephone.
The maximum distance that can be posted, your system depends on the squares of the transmitting and receiving mirrors, ULF sensitivity, atmospheric conditions and angle of declination of the Sun.
Hottelephone can be improved. For example, to increase its sensitivity using a light-proof screens and baffles to eliminate light reflection and glare, or add a preamplifier that increases the signal level from the photocell. Then your system will be able to act at a distance of several kilometers.
L. MOROZOVA
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