I have always had an interest in subscriber loudspeakers (CA). They were produced in all sorts of shapes and colors in the former USSR! Now these products are smoothly migrating to flea markets, where they can often be seen and, most importantly, bought inexpensively. Inside the case, as a rule, there is a transformer for matching the alternating voltage of the broadcasting network (~ 30V) of the audio range with the resistance of the speaker coil (often 8 ohms 2 W). The domestic industry also produced more “sophisticated” versions of AG for two or three channels of wired broadcasting. Currently, three-program wire broadcasting has been introduced in almost all populated areas. Programs 2 and 3 are transmitted at carrier frequencies of 78 and 120 kHz with amplitude modulation. To transmit these programs, wired broadcasting stations are equipped with special transmitters.
I was attracted to AG not so much for its original intended purpose, but for the sake of the housing, where a fairly large electronic device can be built in. And dynamics with a transformer, at the same time, are not difficult to find a use for, teaching the device to sing, talk or make sounds. This is what such a device with a built-in microcontroller board and LCD might look like (Figure 1).
I remember making an apartment bell with a melody and additional functions, such as: determining “friend or foe” by the manner of pressing the button, turning on the corridor lighting, when the door opening sensor is triggered, and some others, which to this day cannot be found in purchased products.
But one day I came across an unusual AG. In addition to the standard variable resistor matching transformer and speaker for such products, it contained an electronic board, the purpose of which was difficult to understand at first glance. After googling, I came across a website of Kazakhstani radio amateurs: Kazakhstan computer portal - Articles Calling device UV_2_14 UHL4_2, USSR.htm. (see attachment). The material is quite informative and sufficiently illustrated, for which we thank its author, Mikhail Dmitrienko. I was somewhat offended by Mikhail’s expression: “The plant was destroyed“, since in my memory I don’t remember that such an expression was used for Soviet electronics production facilities located on the territory of the Russian Federation. Here, much more often, the democratic, so to speak, term was used “ fell apart"...Well, okay, in general, there was a desire to study this pearl in more detail electronics industry Kazakh SSR, especially since I had several of these AGs at my disposal and, naturally, there was a desire to use them “to the fullest”!
As a result of the research, the diagram in Fig. 2 appeared.
Rice. 2
Not being particularly competent in the field of passive filters, I can say that testing with a generator showed transmission of frequencies near 16500 Hz to the detector on the VD1 diode. Pressing the SW button results in a siren-like sound being heard in the small speaker, which is understandable, given the presence of positive feedback using resistor R10. When the resistance of potentiometer R3 is reduced, the generation of a frequency of 1100 Hz of the generator on transistor VT1 also occurs (it is possible that the circuit on this transistor is an active low-pass filter), which, apparently, with this decrease, switches from amplifier to generator mode. Unfortunately, it was not possible to reproduce sounds when modulating the 16500 Hz carrier with any frequencies of 30-3000 Hz from the low frequency range, which was originally expected. What is the “trick” here, perhaps, will be answered by the corresponding topic on the forum, but for now it would be useful to imagine how this circuit could be useful when applied partially or completely, “as is,” using a modern element base.
- The circuit can be used as a digital data receiver with a carrier frequency of 16500 Hz modulated by UART at speeds of 2400-100 baud. By increasing the carrier frequency, the required filter bandwidth can be shifted to 60-50 kHz (which is achieved by replacing capacitors C1, C2, C3, C4) and the reception speed of such data can be increased.
- By adding appropriate matching devices in the form of HF transformers on this base, you can organize a modem for transmitting digital information through the wires of both the subscriber radio network and ~220V power wires, thus implementing a transponder for transmitting information through these interesting communication channels.
- Finally, using the direct conversion technique, for example, described in the literature [2], it is possible to implement radio modems on the basis of this board for communication at convenient frequencies in the HF and VHF amateur radio bands, since it is for transceivers of this kind that a high-quality block of low-pass filters is critical.
Despite the widespread use of FM radio broadcasting, with its excellent quality of sound reproduction and stereo, in my opinion, it is too early to write off the technology of a traditional radio broadcast network. Both residential and non-residential buildings were equipped with it, and probably still are, in accordance with the current SNIPs. This means that the corresponding wires (like the well-known “noodles”) were laid by the projects and laid in the interblock spaces of high-rise buildings. Often, radio broadcast network wires have also been preserved in villages or remote towns, where FM broadcasting may be completely absent. There, the wire lines for the AG still coexist on common poles with the intra-village electrical wiring (even in the form of a field wire twisted into a pair, mounted on miniature insulators). The use of this “bonus” from the Soviet past can now be more diverse and include a low-performance information communication channel, as well as a highly important functions security and fire alarm systems and transmission of emergency alerts.
NOTE: All inductances in the diagram are non-standard, wound on cup cores made of ferrite of an unknown brand, the inductances were measured experimentally and are indicated on schematic diagram. All permanent resistors are MLT brand 0.5 W with the values indicated in the diagram. For a description of the dynamic heads, see the attachment.
Literature:
- Eng. V. Bazylev, engineer G. Skrobot, Three-program loudspeaker, Zh. Radio No. 1 1971
- Polyakov V.T. Radio amateurs about direct conversion technology, Publishing House of the Central Committee of DOSAAF USSR “Patriot”. 1990
- Kazakhstan computer portal - Articles Calling device UV_2_14 UHL4_2, USSR.htm
List of radioelements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| VT1, VT4 | Bipolar transistor | MP41 | 2 | To notepad | ||
| VT2, VT3 | Bipolar transistor | KT315B | 2 | To notepad | ||
| VD1 | Diode | KD103V | 1 | To notepad | ||
| VD2-VD5 | Diode | D104 | 4 | To notepad | ||
| D | Zener diode | KS407A | 1 | To notepad | ||
| C1 | Capacitor | 620 pF | 1 | Mica | To notepad | |
| C2-C4 | Capacitor | 1200 pF | 3 | Mica | To notepad | |
| C5 | Capacitor | 47 nF | 1 | To notepad | ||
| C6 | Capacitor | 2.2 nF | 1 | To notepad | ||
| C7 | Capacitor | 68 nF | 1 | To notepad | ||
| C8, C9 | Electrolytic capacitor | 20 µF | 2 | To notepad | ||
| C10 | Capacitor | 4.3 nF | 1 | Mica | To notepad | |
| R | Variable resistor | 68 kOhm | 1 | To notepad | ||
| R1 | Resistor | 240 kOhm | 1 | To notepad | ||
| R2 | Resistor | 1.3 kOhm | 1 | To notepad | ||
| R3 | Trimmer resistor | 6.8 kOhm | 1 | To notepad | ||
| R4 | Resistor | 68 kOhm | 1 |
FAQ from English Frequently Asked Questions. Dear colleagues. Until the completion of the project reconstruction:
For additional and timely information on the materials of this publication, we ask you to use requests by e-mail: [email protected]. Or ask them on the blog: http://blog.radiouzel.com/
Thanks for understanding.
HOW TO CHECK OLD WIRING?
If you connect TU 200 to existing broadcast lines, then check their quality.
How to check old wiring? Very simple:
To test the old wiring, you can use any transformer from an old tube TV (incandescent winding) or a similar one from a 30-50 W power supply as a step-down transformer.
Make sure “by ear” that each column, loudspeaker, subscriber device hums (you can also check all connection points with one loudspeaker at a new facility) like a 50 Hz transformer. Replace or disconnect the faulty loudspeaker. Lines that do not carry a signal to a known-good speaker should be replaced.
VERY IMPORTANT! LIMITER
Not included in TU 200! However, it is very important! In order to reduce the impact of short circuits in subscriber radio wiring on the operation of the entire radio broadcast network, it is advisable to supply each subscriber point with limiter.
Limiter is a device (resistor) that passes only such current as is necessary for normal operation of the loudspeaker. As a Limiter, for example, you can use universal box(plinth) shown in the figure.
a
— top view with the cover removed;
b
— bottom view with the gasket removed;
1 — plastic body;
2 — holes for fastening the box;
3 - contact screws;
4 - jumper made of bare wire when using a boundary box as a distribution box;
5 - the same in an insulating tube;
6 — recesses for resistors when using the box as a limiter.
The limiter is installed at the very beginning of the subscriber wiring when it branches off from the common line. At short circuit or if an electrical appliance is accidentally plugged into a radio socket, the amount of current consumed by the subscriber point would have to increase sharply. At the same time, the amount of current flowing to the remaining subscribers would decrease and their transmission volume would drop. But the limiter, preventing too much current from passing through the subscriber wiring, thereby alleviates the consequences of a short circuit.
DETERMINING THE NUMBER OF LOUDSPEAKERS
- 1 UAH 300- For office premises, typical classrooms (classes), libraries, teachers' room;
- 6GRN 310- for corridors (1 piece per 15 m), recreation areas, canteens (2 pieces each), gyms (6-8 pieces), large classrooms;
- 10 UAH 321- for assembly halls (4 pcs.), large dining rooms (2 pcs.), noisy rooms (workshops, etc.);
- HD 310 (HS1A) - for the street.
Don't you want to figure it out? There is a (recommended) initial “basic package” for you.
Very important!
When calculating the number of subscriber loudspeakers, the following should be taken into account:
- 6GRN 310(1 piece) = 2 x 1 UAH 300(2 pcs.)
- 10 UAH 321(1 piece) = 4 x 6 UAH 310(4 pcs.) = 8 x 1 UAH 300(8 pcs.)
- HD 310(1 piece) = 3 x 10 UAH 321(3 pcs.) = 12 x 6 UAH 310(12 pcs.) = 24 x 1 UAH 300(24 pcs.)
Thus, to the maximum TU 200 (TR 200) you can connect up to 180 pcs. 1 UAH 300, up to 60 pcs. 6GRN 310, up to 16 pcs. 10 UAH 321 or up to 6 pcs. HD 310.
CONNECTION DIAGRAM FOR SUBSCRIBER AND FEEDER LINES
The system of lines, together with subscriber inputs and radio points, used to transmit broadcasts from the station part of the radio node to subscribers is called radio broadcast network.
There are subscriber and feeder lines. A subscriber line is a line to which subscriber loudspeakers are connected directly using subscriber inputs - as shown in the diagram of a subscriber line with radio points.
Where:
1 — broadcast radio node TR 50; 2 — input wires;
1GNR 300; 4 - subscriber line.
As you can see, subscriber speakers are connected to both wires of the subscriber line, which receives power from the amplifier of the radio broadcasting unit. The speakers will only work if the circuit for electric current audio frequencies are closed. If one subscriber input wire breaks, the loudspeaker will stop working. Therefore, it is necessary to monitor the health of the electrical circuit.
Subscriber loudspeakers used on radio broadcast networks, in accordance with the requirements of Russian standards, use a voltage of 30 V for normal operation. Therefore, 30 V is supplied to the input of the subscriber line. If the voltage in the line is less than 30 V, the subscriber loudspeakers sound quieter, if the voltage in the line more than 30 V, the sound will be too loud and may be accompanied by sound distortion.
As you move away from the station part of the radio node, the voltage in the line will usually decrease. This phenomenon is called line voltage attenuation. The amount of attenuation mainly depends on the length of the line, the number of loudspeakers turned on, the diameter and material of the line wire (the attenuation will be greater the longer the line, the more loudspeakers are turned on and the thinner the line wires). In a correctly calculated subscriber line, which has a voltage of 30 V at the beginning, the voltage at the end should be at least 19 V.
In order not to exceed the normal voltage attenuation in the line, only a certain number of subscriber loudspeakers can be connected to it, namely:
When connecting subscriber loudspeakers to the network various types- the norm is reduced by half.
In practice, there are often cases when it is necessary to connect more radio points to a subscriber line than are allowed by the norm, or it is necessary to radio several groups (directions) of subscriber lines located at a considerable distance from the radio node. If you overload one subscriber line, the attenuation will increase, the voltage at the end of the line will drop significantly and the subscriber speakers will sound quieter. The same result will occur if the subscriber line is too long.
For radiofication of objects remote from the radio node or distribution to several groups of subscriber lines, there are feeder lines. They differ primarily in the voltage of 120 V. They are connected to the 120 V output of the amplifying equipment of the radio node, and at the point where they are connected to the subscriber lines, a step-down transformer of the TAMU type is installed, which lowers the voltage from 120 V to the required 30 V.
Where:
1 — broadcast radio node TR 50; 2 — input wires;
3 — subscriber loudspeakers 1GNR 300; 4 — subscriber line;
5 - feeder line; 6 - step-down feeder transformer.
As can be seen from the diagram, subscriber loudspeakers are not connected directly to the feeder line; they are connected to subscriber lines. Subscriber lines are connected to the feeder line through step-down transformers to reduce the feeder voltage to 30 V. They are usually installed at the remote end of the feeder line in subscriber line connection panels.
RADIO POINT. CALLER LOUDSPEAKER
Subscriber loudspeaker is an electroacoustic or mechanical device used to loudly reproduce a sound signal. Subscriber loudspeakers convert an electrical signal into sound waves propagating in the air using a mechanical moving system (diaphragm or diffuser). Sometimes the term “Subscriber device” is used.
The main types of loudspeakers used in radio centers:
- wall speakers
- ceiling speakers
- horn loudspeakers
We can continue with the technical description and description of the differences, but for our purpose this is not important.
It is important to pay attention to the electrical circuit diagrams of subscriber loudspeakers:
Electrical circuit diagrams of subscriber loudspeakers.
Where:
X - fork; R—resistor; VA - loudspeaker head; TV - transformer
The main difference between subscriber loudspeakers is the presence of a matching transformer (TV). This is very important. Why? The presence of a matching transformer allows you to turn on any subscriber loudspeaker, regardless of the output power, by one " train» appropriate voltage (30 or 120 V - permitted by GOST). Anywhere" plume"How you plug in any of your devices that require power into any electrical outlet anywhere in your apartment. According to the diagram below.
The main difference between modern subscriber loudspeakers for radio nodes is the way they are connected to the “loop”.
INSTALLING A CALLER LOUDSPEAKER
If you imagine or know specific places (classrooms, corridors, dining room, assembly hall, gym, foyer, outdoor sports ground, swimming pool, area in front of the building, etc.) for broadcasting programs, then you are ready to select and install subscriber devices (loudspeakers).
WHERE AND HOW TO LISTEN TO SCHOOL RADIO SHOWS?
You have been allocated a room for a radio unit or have a place allocated for it in a computer science classroom (office). Install the first loudspeaker next to this room in the corridor. And you are ready to promote the idea of a school radio center to the masses.
And yet, where and how to listen to school radio programs? First of all, in the corridors (on all floors), in the assembly hall, gym, even in the dining room - small broadcast loudspeakers can be installed everywhere.
If some of them have the ability to adjust the volume (principal's office, library, teacher's room) - do not install them at a high height - install them so that you can adjust their volume by standing on a chair.
Don’t forget to “radio” the principal’s office and the teachers’ room first. Whether to install loudspeakers in classrooms is at your discretion; some “construction” work will still be required to lay the cable (wire) to the speaker.
Choose the power of the speakers depending on where they will be installed. Radio broadcasts that are too loud or too quiet are not pleasant. Words become illegible and cause irritation.
The number and type of these loudspeakers primarily depend on the size of the rooms being spoken and their purpose. For example, in a gym it is better to install 6 low-power, small-sized but impact-resistant speakers around the entire perimeter of the gym - instead of two powerful ones (as is usually done). But in the dining room, on the contrary, two will be enough, but more powerful...
Make radio broadcasts everywhere a pleasure to listen to. Walking in the hallway during breaks, having lunch in the cafeteria.
The habit of listening to radio broadcasts “in between” has long been developed among radio listeners. And the more interesting the program, the more attentively they listen to it.
The main types of loudspeakers used in school radio centers:
- wall speakers - ;
- ceiling speakers - ;
- outdoor horn loudspeakers - .
Estimate the required power based on the following considerations:
For small rooms such as director's, secretary's, teachers' rooms, accounting - 0.25 - 1 W.
For small classrooms for 20-30 people, classrooms - 3 W.
For corridors, lobbies, recreation rooms, large classrooms, dance halls, gyms (at least 4) - 6-10 W.
For canteens, very large classrooms, assembly halls - 10-25 W.
COST TU 200
Attention! The equipment manufacturer LLC SKB RA STR provides information on the cost and terms of delivery, discounts only upon request
to your address email: [email protected]! Upon request, information on “expanding” radio units and recommendations for checking “old wiring” are also provided.
Of incomparably greater interest than previously described is a loud-speaking intercom. The easiest way is to use ready-made subscriber loudspeakers for these purposes, which are always available for sale. The design of the loudspeaker does not matter; it is important that it is designed for a broadcast network voltage of 15 V (loudspeakers are available for voltages of 15 and 30 V); the loudspeaker manages to obtain the highest volume.
In total, for the intercom you need to purchase two loudspeakers, one each for the communication point. As you probably guessed, each loudspeaker will perform both its direct role and the role of a microphone. It is not difficult to understand how this is achieved if you look at the diagram (Fig. 1) of the intercom - it is somewhat reminiscent of the diagram of the previous design. Before you get acquainted with the operation of the intercom, consider the diagram of the subscriber loudspeaker - it has two new symbols: the so-called direct radiation dynamic head B1 (or simply dynamic head) and transformer T1
Fig.1. Diagram of an intercom with subscriber loudspeakers
When they talk about a dynamic head, they mean this part itself without any additional accessories. If the dynamic head is installed in the housing, this design is already called a loudspeaker. Some other parts can be mounted inside the speaker housing - a transformer, a capacitor. In the loudspeaker shown in the diagram, you see a low-frequency transformer T and a variable resistor R. The transformer is needed to connect the dynamic head to the broadcast network, and the variable resistor controls the volume of the loudspeaker. In the intercom, the loudspeaker is used in maximum volume mode, when the variable resistor slider is in the upper position according to the diagram and winding 1 (primary, high-resistance) of the transformer is connected directly to the pins of the plug with which the loudspeaker is connected to the broadcast network.
So, the loudspeaker is connected via connector X1 to the input of an amplifier assembled on transistors VI, V2. But it is connected somewhat differently compared, for example, with the capsule of the previous design - one of the speaker terminals is connected not to the common (positive) power wire, but to the negative one. This was done specifically to simplify the loudspeaker switching circuit and reduce the number of switch sections. But via alternating current, that is, an audio frequency signal, it is still connected to the emitter of transistor VI through capacitor C4 and the GBI power supply.
The input and output of the amplifier are connected to switch 51. In the position shown in the diagram, the subscriber loudspeaker is connected via a switch to sockets X2 and X3, which are connected through a communication line to the same sockets of the second device. Thus, as in the previous intercom, the loudspeakers of both devices are connected to the communication line. If now the switch of the first device is switched to the “Transmit” position, the loudspeaker will be disconnected from the communication line, and the amplifier output will be connected to it. At the same time, the lower contacts of the switch (3 and 5) will close and supply power to the amplifier. The loudspeaker will become a microphone. Sound vibrations are first converted by it into electrical signals, which are then amplified by transformer T and an amplifier. The amplifier's output signal is fed through a communication line to the loudspeaker of the second device, where the reverse process occurs - the electrical signal is converted into sound vibrations in the air. These vibrations are heard by the subscriber.
In the diagram, as you can see, there is no call button, since there is no need for it - the sound volume is sufficient for the voice to be heard anywhere in the room. Switch S1 must be taken the same as in the previous intercom, or made from two single toggle switches of type TV2-1. Transistors MP39B, MP41, MP42A or MP42B with a current transfer coefficient from 40 to 5. Capacitor C can be of the MBM type or any other capacity from 0.1 to 0.5 μF; SZ also of any type (KSO, K40P-2, BM-2, PO, PM-1, etc.); C2 and SA type K50-6, K50-12 or other electrolytic capacitors with a capacity not less than that indicated on the diagram, and with a voltage of at least 10 V. Resistors - MLT-0.25 or MLT-0.5. Power battery GB1 - two series-connected batteries from a 4.5 V flashlight (type 3336L). It is not advisable to use a Krona battery due to the relatively short service life with this amplifier (3-4 hours continuous operation). The subscriber loudspeaker can be, for example, “Surprise-301” with a voltage of 15 V. To connect it to the device you will need a response socket XI. Sockets X2 and X3 of any design (this can be the same socket as for connecting a loudspeaker).
The device parts are placed on a circuit board made of insulating material (Fig. 2). The batteries are placed on top of each other and secured to the board with a metal bracket. The switch is secured with a nut so that the threaded part of its body protrudes 7-8 mm above the surface of the board. To solder the pins of the parts, it is necessary to install mounting studs on the board made of thick tinned wire; the ends of the studs should not protrude more than 3 mm from below - they are shortened with wire cutters upon completion of installation. At the corners of the board, small spacers made of cardboard or plywood 3-4 mm thick are glued to the side of the switch handle and holes are drilled in them opposite the holes in the board. The board with the parts is installed in a housing (Fig. 3) with a removable bottom cover. On the front panel of the case you need to cut holes for the connector, sockets and switch. The board is attached to the front panel with screws, and the switch body is fixed to the panel with a nut.
Rice. 2. Interphone circuit board
Now is the time to check and, if necessary, adjust the intercom apparatus. But first, as usual, you need to carefully check the correct installation and reliability of all soldering. Then you should connect the wires of the communication line with the loudspeaker at the other end (in other words, in another room) to the X2 and X3 sockets. Insert the plug of “your” loudspeaker into socket X. Place the switch knob in the “Transfer” position and measure the voltage between the emitter and collector of transistor V2 - it should be in the range of 3.5-4 V. If necessary, you can set this voltage more precisely by selecting resistor R3. In the same way, check the voltage between the collector and emitter of transistor VI and, if necessary, set its value within 3-4 V by selecting resistor R1. You can verify the operation of the device by listening to the sound from the second speaker. This is where you need an assistant: let him speak in front of a loudspeaker-microphone, and you listen to his voice in another room. You will probably have the idea that you can do without an assistant if you install a second loudspeaker in the same room not far from the device and listen to yourself or, in extreme cases, clapping your hands. But in most cases, this test fails due to the acoustic coupling between the speakers. If they are located in the same room, a sharp whistle may appear in the second speaker and no other sounds will be heard.
True, there is another way to check the device without an assistant. Place a transistor radio tuned to a station in front of the loudspeaker-microphone and listen to the sound in the second loudspeaker. If side sounds are observed in the form of a weak whistle or excessive hissing, replace the SZ capacitor with another, larger capacity (350, 3900, 4300, 4700 pF). It is even better to do this. Place the receiver near the second speaker (it is in another room), set the device switch to the “Receive” position. Connect “your” loudspeaker between pins 5 and 6 of the switch (that is, connect the pins of the loudspeaker plug with conductors to the output of the amplifier), and temporarily short-circuit pins 3 and 5 of the switch with a wire jumper. Now the second speaker will serve as a microphone, and through “yours” you will be able to control the sound. The variable resistor knob on each speaker must be in the maximum volume position, otherwise nothing will work.
Intercoms, diagram, description, for self-assembly
Rice. 3. Appearance of the intercom
It may happen that the device uses transistors with a high transmission ratio and the sensitivity of the amplifier is excessive, which is why the sound is loud and distorted. It is not difficult to reduce the sensitivity of the amplifier by connecting a variable resistor with a resistance of 22-68 kOhm in series with capacitor C (Fig. 4). Set the desired volume by moving the resistor slider, measure the resulting resistance with an ohmmeter and solder in a constant resistor with the same resistance (or possibly close) instead of a variable resistor.
At this point, checking and setting up one device can be considered complete and we can begin assembling the second. Do not forget, of course, to remove the jumper from pins 3 and 5 of the switch, unsolder the speaker pins from the amplifier and insert the speaker plug into connector X. Having made the proposed set-top boxes, you have not affected the speakers themselves, and they can be operated from the broadcast line at any time - for All you need to do is move their plugs into the appropriate socket. If you want to make a permanent intercom, it is better to mount the electronic part of the device inside the loudspeaker - the design will be more compact. Of course, there is not much space in the speaker housing and you will have to slightly change the placement of parts and installation. So, the circuit board should now be smaller (Fig. 5), and the switch and amplifier parts are placed on it. The board must be attached to the top wall of the case (Fig. 6) so that the switch handle comes out. Opposite the positions of the handle, glue strips of paper to the wall with instructions on the operating mode of the device - “Reception” and “Transmission”.
Intercoms, diagram, description, for self-assembly
Rice. 4. Method for reducing the sound volume of the intercom
The power source (two batteries from a flashlight connected in series) can be placed both inside the case and outside - on the removable rear wall made of cardboard. For the last option, make a “pocket” (Fig. 7), for example, from thick cardboard or paper glued in several layers. Attach (or glue) the “pocket” to the back wall, install the batteries in it, connect them in series (as shown in the figure) and solder the ends of the device’s power conductors passed through the holes in the wall to the terminals.
Intercoms, diagram, description, for self-assembly
The rest of the installation of the device is also simplified. Now connector X1 is no longer needed; solder the conductors from the board intended for it to the extreme terminals of the variable resistor of the speaker. Separate sockets XI and XZ also turn out to be superfluous; their role will be played by the pins of the loudspeaker plug. To avoid confusion during installation, first unsolder the ends of the speaker cord from the terminals of the variable resistor. Using an ohmmeter or a simple probe consisting of a light bulb, a diode and a battery, which was described above, determine which pin one or another end of the cord is connected to, mark them and solder the ends of the cord to the corresponding points on the circuit board. Make the inscriptions “X2” and “XZ” on the plug opposite the pins - they will help to correctly connect the device to the communication line. To connect devices at the ends of the communication line, install sockets with marked sockets (X2 and X3) and insert speaker plugs into them. The procedure for setting up devices remains the same.
Intercoms, diagram, description, for self-assembly
Rice. 6. Appearance of the subscriber loudspeaker with intercom
In some cases, it may be necessary to have a one-way intercom, that is, one where the first subscriber can call the second or say something to him, but the latter cannot call the first. This is necessary, for example, if you have been asked to look after a baby who is sleeping or in the next room. An intercom will help you hear your baby’s cries in time to calm him down. With this version of the intercom, the central apparatus (let's call it that) is installed in the parents' room or in the kitchen, and only an additional loudspeaker is placed in the baby's room. The switch on the central unit must always be in the “Receive” position. The loudspeaker in the baby's room is connected to the input of the amplifier, and the loudspeaker central office- with his release. As soon as the baby cries or becomes capricious (this will be clearly audible even at a distance of several meters from the device), it is enough to move the switch to the “Transmit” position, speak a few words in front of “your” loudspeaker, and maybe even talk to the baby at a distance, alternately moving the handle switch to one position or another.
Intercoms, diagram, description, for self-assembly
Rice. 7. Placement of the power supply on the rear wall of the speaker
Fig.8. One-way intercom circuit diagram
The design of such a device is somewhat different from that discussed earlier. The two-section switch is now not connected to the power source and only works to switch the speakers to the input or output of the amplifier. The power source must be a mains rectifier with a voltage of 9 V (such devices are sold in radio stores or in the radio sections of department stores). At the end of using the device, remove the rectifier plug from the power outlet and de-energize the amplifier. To reduce the constant listening noise (background AC), which may appear when the amplifier is powered from a rectifier, you need to increase the capacitance of capacitor C4 to 500-1000 µF.
You can, of course, still power the amplifier from batteries, but turn on the amplifier for a short time, remembering that the total service life of the batteries with this amplifier is no more than 15 hours. There is another power option, especially convenient when operating the amplifier outdoors, when there is no power outlet nearby. Use as a source battery 7D-0.1 with a voltage of 9 V. In the evening it is recharged from the mains using a charger (it is sold in radio stores). The power source can, of course, be made up of more powerful batteries, for example, from motorcycles. Use as many series-connected cans as provide a constant voltage of 8-10 V. Charger for such a source should be designed for a current equal to approximately 0.1 battery capacity.
Pocket MP-3 players with flash memory they are very convenient, they are small in size, the size of the memory allows you to store many audio files, and the sound quality is quite good. One problem - they only work on headphones. If you have two extra “radio points” (subscriber loudspeakers), you can make two active ones out of them speaker systems for loud-speaking playback of music from an MP-3 player.
The subscriber loudspeaker usually contains a speaker, a transformer and a volume control.
A “typical” circuit of a subscriber loudspeaker is shown in Fig. 1.
If you simply connect such a subscriber speaker to the telephone output of an MP-3 player, it will, of course, sound, but very quietly, about the same as if you put headphones in front of you. For more or less loud sound, you need to add at least a simple low-frequency amplifier to the subscriber speaker circuit.
Figure 2 shows two transistors.
The sound volume with such ULF will be approximately the same as that of a portable radio. And as a power source you can use a 9V battery or any mains source DC voltage from 8 to 15V, for example, a power supply from a television game console such as “Dandy” or “Kanga”. Well, or some other one, maybe a power supply for some computer peripherals, or a universal one for powering portable equipment. The main thing is not to confuse the polarity of the connection!
As can be seen from the diagram, the bass amplifier is connected between the volume control, which is in the subscriber loudspeaker, and its transformer. The amplifier is two-stage, using transistors of different structures with direct coupling between the stages.
The signal from one of the stereo channels of the telephone output of the MP-3 player is supplied to the “Input” connector, which is installed instead of the wire through which the subscriber speaker was connected to the radio network. Through it, the signal goes to the variable resistor “R” - the volume control of the subscriber loudspeaker. Next, through circuit C2 - R1 to the first amplifier stage on transistor VT1. This transistor operates according to a common emitter circuit. The second stage on transistor VT2 is a power amplifier, it is connected directly to the first, and operates according to a circuit with a common collector.
The operating mode of the amplifier as a whole is determined by the resistance of resistor R2. In this case, the capacitor SZ suppresses self-excitation by high frequencies and RF interference from the operation of the ADC of the digital signal source (MP-3 player).
The load of the amplifier is the primary winding of the transformer T, through which power is supplied to the amplifier.
The amplifier is assembled on printed circuit board, shown in Figure 3.
Any payment can be made in an accessible way. For example, transfer the hole location points to a foil fiberglass workpiece, then drill the holes. Then draw printed paths with a marker for writing on glass. And then, etch in a solution of ferric chloride.
Details. Capacitor C1 type K50-35 or an imported analogue, for a voltage of at least 10V. Transistors KT3102 and KT3107 can have any letter indices.
The connection diagram is shown in Figure 4.
Thus, a single-channel active speaker system is obtained. You can apply a signal to its input from one of the stereo output channels of the MP-3 player. To listen to stereo, you need to make two such speaker systems, preferably from identical subscriber loudspeakers.
It is convenient to supply the signal to the inputs of two speakers through a wire from faulty stereo headphones.
While sorting out my grandmother's things, I came across a wired radio (subscriber loudspeaker), which served faithfully for about 30 years. Of course, it cannot be called an outstanding creation of Soviet industrial design, but it would be a shame to throw it away.
On the other hand, where can it be applied? There is no subscriber radio point in my apartment, and I have no particular desire to listen to national radio broadcasts. If only you could listen to what you want and it’s like on the radio... And, actually, why not? And then I came up with the idea of making a regular speaker out of a subscriber loudspeaker! Well, that is. an ordinary mono speaker connected to a sound source through an amplifier.
What did I get?
To determine the device model, we had to search by appearance with complete search, because neither the name of the model nor the manufacturer was listed on the case. Fortunately, the search was short-lived - I got the Donbass subscriber loudspeaker.
In my case, however, it is black and yellow, without a handle, without a back wall, without a plug and with a twisted wire.
Modernization plan
The essence of the upgrade is to integrate the amplifier into the speaker housing and connect any sound source to the input. The issue with the amplifier was resolved quite simply: remove it from unnecessary Chinese Taiwanese speakers.
It should be noted that using an amplifier made from Taiwanese speakers is not the best option in terms of sound quality, but it is the simplest and cheapest (provided such speakers are available).
The main issue of modernization was the sound source. You can connect anything to the input: portable radio, player, phone, laptop. At the same time, I didn’t want to clutter the device functionally, but on the contrary, to make it as simple and convenient to use as possible. A good option It might be possible to use the AirPort Express audio output, but it is already in use, and I didn’t want to buy another router. The best option was found unexpectedly.
It was decided to hang the loudspeaker in the kitchen on the wall where the TV was originally planned to be hung. There were regular and TV sockets for the TV, and the TV cable from the socket goes to another room to a single cable switching point for the TV and modem.
What if you send sound through a coaxial cable from the room to the kitchen? From the room I connect everything I want, and at the output I simply amplify the sound. It’s clear that coax is far from oxygen-free copper, but I’m not going to listen to hi-fi over a loudspeaker.
Modernization
Well, let's get started. Of the three parts in the loudspeaker housing: speaker, variable resistor and transformer, we leave only the speaker. More precisely, you should first remove all the parts, wash off the taint of stormy youth from the body and then insert back only the necessary ones. I want to warn you right away: The loudspeaker speaker produces sound in the range of approximately 160-6300 Hz, so if you are going to listen to your favorite music through such a speaker, then it will sound at least not entirely authentic.We disassemble the Taiwanese speakers: from the one with the volume control, we remove the board and transformer. In my case, the speaker in the column was not soldered, but connected through a connector. We unsolder the wires together with the connector from the speaker and solder them to the speaker speaker. The transformer from the speakers also has a connector, and therefore practically without any problems it replaced the previous one in the speaker housing. Let's move on to the board.
We unsolder the second column (wires on the left), and instead of the wires from the jack (on the right), we solder the original wire from the subscriber device. The main thing here is to find which channel goes to the speaker and solder to it. The second channel can be grounded. Next, we unsolder the variable resistor, and in its place we solder three wires (again, from the side of the channel going to the speaker).
We solder these wires to a variable resistor of the same value, but with a switch. And we attach the variable resistor itself to the place of the previous one in the housing. The switch will serve as a button to turn on the amplification circuit. As a result, when you turn the control knob, the amplifier will first turn on, and then the volume will be adjusted. Interestingly, the amp switch on the speakers I used is located after the transformer. Those. when these speakers are connected to the network, regardless of whether the circuit itself is turned on or not, they consume their two watts. Actually, that’s why I installed the switch not instead of a button, but in front of the transformer.
I attached the board and power connector to the case with silicone glue, and chose the most suitable one from old Soviet pens. As a result, this is what the loudspeaker looks like from the inside:
And this is from the outside:
Let's not forget about the sockets: we replace the standard white ones with black and yellow ones that are more suitable in color:
Switching point (adapter: coaxial - monojack, extension cord: female jack - male jack):
In progress
In operation, a regular subscriber loudspeaker behaves well - it regularly reproduces the sound supplied to the input, coloring it with the effect of a wired radio. Automatically, the sound source in the form of a laptop became the director's console, because When you connect a microphone, you can broadcast from the room to the kitchen: send greetings, play your favorite music, and also communicate with radio listeners. The only downside that can be noted is the characteristic background of the amplifier made from cheap Taiwanese speakers.Behind the director's console.