Telephone- This electrical device, allowing people to exchange information over a distance using an electrical signal. The word telephone came to us from ancient Greece. Tele is translated as “far”, and background is “voice”.
After reading the article, any home craftsman can easily connect a landline, fax, or several parallel telephones, including a radiotelephone.
What is the voltage in the telephone line
The telephone communication line is under a DC voltage of 40-60 V if the telephone is not connected or is connected, but the handset is placed on the telephone set. During a call, the voltage in the communication line becomes variable with an amplitude of up to 120 V. When you pick up the phone, the voltage drops to 6-12 V. This voltage is not life-threatening, but it can cause discomfort.
It is impossible to damage the communication line or damage the telephone when connected. The telephone line may be disconnected for several minutes if the handset is lifted for a long time without dialing a number or if the communication line conductors are short-circuited. The telephone line is automatically switched off by an automatic telephone exchange (PBX) to save energy. So you can safely start self-connection telephone to the communication line.
Before connecting a landline telephone, fax or radiotelephone to the communication line, it is advisable, but not necessary, to check that the communication line is ready. The line voltage can be measured with a voltmeter designed to measure DC voltage.
If the phone is not connected to the line or is connected, and the handset is on the phone, the device should show a voltage of 40-60 V. If there is no voltmeter, you can check using a potato, and this is not a joke, but real way checks. It is enough to stick the noodle wires, stripped of insulation, into the cut of the potato. No batteries are needed since the wires are already energized.
What current will flow
in case of short circuit of telephone line wires
The PBX is equipped with a protection system against failure of equipment and communication lines, which limits the current during a short circuit of the telephone line to 40 mA.
For the communication line, one of the free pairs, brown or blue, is taken. twisted pair consists of two conductors twisted together. The insulation of one of them is painted a solid color, and the insulation of the second is white with stripes of the color of the first.
Having two telephone sets, a coil of two-core wire of sufficient length and a small number of radio components, you can organize your own telephone line for two subscribers. For example, arrange a connection between two neighboring apartments by throwing a wire between the windows, or between neighboring country houses, between a house and a gazebo. First of all, let’s remember from our school physics course how a telephone works. In the simplest case, these are two telephone capsules connected to each other by a two-wire line.
When one speaks in front of one capsule, its magnetic membrane moves from sound waves and induces some alternating voltage in the coil, which is supplied through wires to the coil of the second capsule and sets its membrane in motion. It turns out that the membrane of the second capsule moves in the same way as the first, creating sound waves that can be heard. But theoretically, such a connection is ineffective, the losses in the wires are too large and the efficiency of the capsule is low.
Therefore, a real telephone set has a carbon microphone, the resistance of which changes in time with speech. In addition, some constant pressure. The result is that a carbon microphone connected to the line, changing its resistance in time with speech, causes a change in the current strength in the line.
Thus, an alternating current is obtained in the line, which changes in time with speech. This current powers the capsule of another telephone and emits sound waves that are quite distinct and loud.
A schematic diagram of a simple telephone line is shown in the figure. Two electronic telephone devices are used - handsets with push-button dialers, but you can also take simple ones
disk devices. They are connected to each other by two wires. These wires are supplied with a constant voltage of 60-80V through resistance R1. When the tubes of both TAs are hung between these wires, there is a voltage of 60-80V, since in this state internal resistances TA is very high.
Suppose we pick up the handset TA2, while its lever switch connects its conversation node to the line and the resistance of TA2 decreases sharply, so much that the voltage in the line drops to 8-10V (the voltage drops because from the resistor R1 and the resistance of the conversation node TA is obtained voltage divider, and the line turns out to be connected precisely through this divider).
If you start speaking in front of the TA2 microphone, the resistance of its conversation unit begins to change in time with the speech, which means the overall resistance of TA2 also changes. In this case, R1 remains unchanged and the voltage in the line changes in time with speech. The TA1 telephone is also connected to this line, and if you pick up its handset, you can hear what is being said in front of the TA2 microphone. If subscriber TA1 answers, subscriber TA2 will hear his voice. This way you can talk to each other.
To call a subscriber, the telephone set has a bell or buzzer; it is connected to the line whenever the handset is hung up and reacts to any significant voltage drop in the line. If you pick up TA2, the TA1 bell will “ring” once, because there was one voltage drop in the line, hang up and TA1 will “ring” again.
The telephone station contains a dialer, push-button or rotary, it doesn’t matter, in any case it serves to create voltage drops in the line; the telephone exchange receives these drops, counts them and thus determines the subscriber’s number. In our case, there is no telephone exchange, but the dialer can be used to call a subscriber. If you dial the number “9”, the TA creates nine voltage drops in the line, which means that the second TA “rings” not once but nine times, if the number “0” - ten times.
Thus, in order for you to call your friend on TA1 from the TA2 phone, you need to pick up the TA2 handset and dial “O” (or another number) several times in a row. As a result, TA1 will ring, your friend will hear the call, and by picking up the phone he will be able to talk to you. In the same way, you can call TA2 from the TA1 device.
The constant voltage for powering the line is obtained from the 220V mains voltage using transformer T1 and a rectifier using diodes VD1-VD4. Rectified voltage ripples are smoothed out by capacitor C1. Transformer T1 can be made from a small-sized transformer from a network source to power toys or portable equipment. It is necessary to disassemble the source housing and connect the transformer using an extension cord to the network and measure the voltage on its secondary winding. Let's assume the voltmeter shows 6V.
We need 50 V. Now we disconnect the transformer from the network, disassemble its plate core and unwind the secondary winding (not the mains winding), carefully counting its turns. Let's say we counted 120 turns, this despite the fact that the output voltage was 6V. Now we calculate how many turns this transformer has per 1V: 120 / 6 = 20, a total of 20 turns. We need 50 V, which means the secondary winding must contain 20x50 = 1000 turns. We take a thin winding wire, for example PEV 0.06 or PEV 0.09, and carefully wind 1000 turns with this wire instead of the old secondary winding.
Then we assemble the transformer core. You can take a ready-made transformer that produces at least 36V and at most 50V.
D226 diodes can be replaced with any rectifier, for example D7 or modern KD102, KD103, KD105, KD226, KD209. Capacitor C1 for a voltage of at least 100V and a capacity of at least 160 µF. Resistor R1 with a resistance of 1 kOhm to 1.8 kOhm for a power of at least 2 W. Toggle switch S1 of any type.
Structurally, the power supply can be connected to the line anywhere, near TA2, near TA1, or even in the middle. For example, if TA2 is in an electrified room, and TA1 is in a garden gazebo, it is clear that the source is connected near TA2.
When installing, do not mix up the polarity of connecting capacitor C1 and diodes. D226 diodes have graphic image diode, along the body, so that you can understand the purpose of the terminals.
Hello, dear lovers of experiments and DIY experiments!
We have already touched on the topic of telephone communication on the pages of the DIY science and technology blog. Back then we were talking about a phone made from plastic cups. Unfortunately, such a phone demonstrates very well some laws of acoustics, but in practice it can only be used in fairly ideal conditions— the telephone thread should be taut and should not touch any obstacles. Yes, and the length of the thread is limited. Another thing is a regular wired telephone. There is no doubt about its applicability. Despite the spread mobile communications, it will not soon be forced out of apartments and offices. We’ll talk about it, and at the same time we’ll build our own simple telephone network, devoid of the above-mentioned disadvantages.
Did you know that telephone communication officially dates back to the 19th century, and since then the basic design of the telephone has remained virtually unchanged? This is true. Of course, the phone has changed in detail - a modern telephone includes electronic components that simply did not exist at the time of its invention. In telephone networks there are automatic telephone exchanges that switch subscribers among themselves. Various telephone services have appeared. However, the purpose of a telephone set of any circuit has remained unchanged since its invention by Alexander Bell in 1876 - converting sound into an electrical signal and transmitting it along a communication line to the desired subscriber and converting it back to sound signal. And in this classic telephone connection there is no equal.
To demonstrate this point, let's compare the above-mentioned plastic cup phone to a regular telephone network. We have already talked about the disadvantages of the first - it is a short range, the absence of obstacles in the path of the communication line, and ensuring thread tension. In addition, let's estimate the speed of sound propagation in the first and second types of communication. Thus, the speed of propagation of a sound wave in iron is approximately 5000 meters per second. Even if we found a way to eliminate sound wave attenuation, sound from, say, Moscow to Vladivostok would take 30 minutes! I don’t know about you, but I would quickly get tired of such a phone - the radio signal reaches Mars faster! Another thing is the speed of propagation of an electrical impulse - 300,000 kilometers per second. There is no better intermediary for sound transmission. You just need to come up with a way to convert a sound wave into an electrical signal and vice versa. And this is exactly the method that Alexander Graham Bell found.
In his telephone set, the sound signal was converted into electrical impulses, which reached the opposite device through wires and were converted there back into a sound signal. Everything turned out to be as simple as it was ingenious! Of course, in the first telephone network there were no telephone exchanges, no dialers, or other modern telephone delights. There were only two telephone sets connected to each other by an electric wire. I suggest you check the possibility of the existence of such a telephone network. Moreover, such telephone communication It is quite possible to use it in practice, for example, to install telephones in a home workshop. And if you take such a phone to your child’s place of play, it will remain a key link in many games for a long time.
So, we will need:
- two telephone sets;
- electrical wire.
- DC source.
- telephone patch cord.
As for the electrical wire - there is no need to limit yourself - any length of telephone wire can be used for your experimental or home needs. The type of wire can also be almost any. In my experiments I used 30 meters of twisted pair cable.
As for the DC source, we can say the following. In the telephone network, the voltage on the line at rest (when the phone is on-hook) is 60 volts. But for our experiments, the voltage from two Krona batteries will be sufficient. You can also use a 12-20 volt power supply.
Take the patch cord and cut it in half.
We clean the ends. The strands of the patch cord are often very thin, and it can be inconvenient to simply strip them with a knife. You can burn them.
If you use batteries, connect them in series. It is convenient to use clip-on contacts, but you can do without them.
We connect our current source to the circuit in series, that is, to the break of one of the wires.
Don't forget to insulate the contacts.
That's it, you can use it! The only significant drawback of this scheme is the inability to call a subscriber. To ensure this possibility, it is necessary either to supply alternating voltage to the line, as is done in city networks, or to install an additional line to provide sound or light calls.
Almost every user of a smartphone or tablet with Android OS sooner or later needs to transfer files from Android to Android? However, not all “users” can connect two modern gadgets and create a reliable data transmission channel.
Therefore, in this article we will take a closer look actual question, how to connect an android to an android, and we will present the four most common and simplest in functionality ways to solve this problem.
How to connect an android phone to android via bluetooth?
- Connect two devices with each other operating system Android is possible using Bluetooth technology.
To transfer files from Android to Android via Bluetooth you need to:
Find in the “File Manager” or “File Directory” the same file that you need to transfer to another Android device;
Click on the selected file and select “Send” from the suggested actions;
A window will open with a list of sending methods. this file: You must select “Bluetooth” accordingly;
By entering the security key, confirm the connection to the device (if required) and wait until the transfer of the file(s) is completed.
How to connect android to android via wifi?
- You can also use a wifi connection to connect Android devices to each other.
Of course, you won’t be able to get by with just a wifi module: to exchange data you will need to download a specialized software(for example, "Fast File Transfer").
However, connecting android to android via wifi has a number of advantages, including:
- - data transfer rate at wifi connection significantly higher than when using a Bluetooth adapter;
- - file sharing can be organized between devices with different operating systems;
- - the ability to use “QR codes” has been implemented.
To connect two Android devices via wifi, you need to download and install the appropriate application, then launch it and follow these steps:
At the first stage, you will be asked to enter a “Device name” - for example, “Proverka” - and a password to establish a wifi connection;
On the list possible ways transfer the file, select “Fast File Transfer”;
Now on the phone/smartphone that is the “receiving” side, and in the search for available access points, select the connection whose name you specified in the first step - “Proverka”, and connect by entering the password;
After a successful connection, the address will be indicated at the bottom of the application window, which must be entered in address bar browser;
After going to to this address the browser will begin to automatically download the file you selected.
How else can you connect an android phone to an android?
You can also use another great app called Filedrop.
In this case, to connect two androids, follow the same initial steps: download the application, install the software (on all devices) and launch. When you first launch the application, you will need to grant access to files, folders, etc.: confirm permission and simply drag and drop required file to the icon of the device where you want to transfer it (smartphone, tablet or computer).
How to connect android to android via internet?
To create and share on a smartphone/tablet, you will need to download and install file manager"ESconductor". Setting up the software consists of the following steps:
Launch the program and select the “Network” section in the menu;
A window will appear with the name of the connected network - click the “Enable” button;
The next step will indicate the address that you need to remember.
It will be needed to synchronize with devices (for example, “199.199.199.199:2233”);
Click "Create" - "FTP"
Now enter the address (“199.199.199.199:2233”) in the “Server” line before the colon sign, i.e. 199.199.199.199;
In the “Port” line, enter the numbers indicated after the colon: 2233;
Click “OK”, open the created folder (with the same name as the address) and select the actions you need (copy/move/delete, etc.).
It is worth noting that this application free and, in addition, includes such features as:
- - support cloud storage(“Google Drive”, “OneDrive”, “Dropbox”, “Box.net”, “Sugarsync” and others);
- - integrated “RAR” and “ZIP” archivers;
- - support not only “FTP”, but also “FTPS”, “SFTP” and “WebDAV”.
It would take a long time to list all the possible functionality, so this application is one of the best solutions for connecting Android devices to Android.
Despite the rapid decline in the popularity of landline telephones, there are not so many people who are ready to refuse them outright. Admit it, it happens that it is sometimes extremely difficult or even impossible to do without a traditional connection.
To connect the device to the switching network, you need a low-current node, the installation of which can be done by yourself. We will tell you in detail how to connect a telephone socket without calling a technician.
There is absolutely nothing complicated in the schemes and methods, and our proposed helpful information, as well as photos and video materials.
The designs of landline telephones are modified and improved every year. AND modern devices significantly superior to their predecessors, standing out favorably due to their high reliability and ease of use.
To ensure uninterrupted operation of the device, two conditions are necessary:
- Availability of an active communication line from the PBX.
- Possibility of electrical connection of a stationary device to this line.
The only thing that does not change in the field of telephony is the principle of operation of landline phones. However, there are significant changes in designs and connection methods.
Old and new telephone switching options are presented in the photo selection:
Image gallery
The following tools need to be prepared for the work:
- building level;
- cross knife;
- voltmeter;
- screwdriver;
- wire cutters;
- graphite pencil;
- protective gloves;
- Double-sided tape;
- hammer drill (if installing a new point).
When choosing a screwdriver, you are guided by the type of surface and dimensions of the screws used for fastening. To minimize the likelihood of electric shock, it is better to perform all manipulations with a screwdriver whose handle is insulated.
Having outlined the installation location of the connection point, use a building level to correct the horizontal and vertical position of its position
To connect a hidden type socket, you must first make a hole in the wall for its installation -. This can be done using a hammer drill equipped with a special crown with a diameter of 60-70 mm.
In the absence of one, the work can be done with an ordinary hammer and chisel. But manual labor will take much more time and effort. Then, to the hole made, it is necessary to drill a channel for laying the telephone cable.
There are certain nuances when installing a socket box in.
Stage #2: Stripping the ends of the cores
Before you start melting the wires, you need to strip the ends of the wires, removing the outer layer. Just expose the outermost 4 cm of the wire.
When stripping a telephone cable, remember that it is very vulnerable to damage. And broken wires will only lead to equipment malfunction. Therefore, it is important to use a specialized one.
Since it is not always possible to carry out the cutting accurately the first time, experienced craftsmen recommend that when laying the cable, make some allowance for its length. The excess wire can then be hidden under the cover of the device.
Removing the protective insulation from the ends of the cable should be done extremely carefully, using a cross-cutting knife, a sharp blade or side cutters.
The technician’s task is to strip the ends of the wires from the braid so that when exposed they are intact and free of any defects.
Step #3: Connecting the outlet wires
Stripped wires with separated cores are connected to the connectors of the box itself, focusing on the markings indicated on the front panel of the indoor unit. At closed method installation, for ease of connection, the wires are made to protrude beyond the wall plane by 50-80 mm.
To maintain polarity when connecting wires, follow the rule: red insulation on the line with the “-” sign, and green braiding on the “+”
If the rules regarding polarity are not followed, there is a high risk that the telephone will malfunction from time to time during operation.
At this stage of work you will need a voltmeter. With its help you need to check the readiness of the communication line. The line voltage should be between 40-60 Volts.
The supplied cable cores are applied to the clamp and tightened tightly with special screws, ensuring reliable fixation. The shape of the grooves to which the cores are attached facilitates the installation process. There is no need to wrap the joints with electrical tape.
When connecting devices whose design is equipped with four fork-shaped contacts, only the two central contacts are used
When performing open mounting, at the final stage all that remains is to close the housing cover using the latch and secure it with screws. The finished socket is attached to the wall or floor, “planting” it with double-sided tape.
With a closed installation method, making sure that the wires are not intertwined in the socket box, according to the markings applied, the indoor unit is mounted into the wall. Having given the block the desired position, the structure is fixed using expansion screws and self-tapping screws.
At the final stage, all that remains is to eliminate the gaps between the socket box and the wall, covering it with gypsum mortar, and also seal the channels with the laid telephone cable.
After the plaster has acquired the desired strength, the protective edging is installed in place and the front panel is attached. In modern devices, the protective edging is snapped onto the internal unit, and the front panel is secured by screwing in screws.
There is nothing difficult about connecting a telephone socket. The only thing is that you should not save money by purchasing equipment in a low price range. It does not always meet the standards and can fail even at the connection stage.
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