It turned out that after the apartment was exchanged, two simple dial telephone sets became superfluous. The new apartment did not have a telephone point, and no one regretted it - everyone had a cell phone. The devices remained in the closet for several years, until it was necessary to organize an intercom between the garage and the country house (both objects are on the same site).

Intercom of 2 telephones

So. a diagram of a typical telephone set is shown in Figure 1. B1 and M1 are the components of the telephone receiver - a carbon microphone and an electromagnetic capsule. F1 - call. S1. S2 is the dialer as long as it is not touched S1 is closed and S2 is open. And when they dial the number

S2 closes, and S1 opens the circuit as many times as the number of units in the dialed digit, for example, turned "9" - opened the line nine times. S3 is a rocker switch. When the receiver hangs up, it is in such a position as in the diagram, that is, it connects a bell to the line. And when we pick up the receiver instead of ringing, he connects the receiver.

The challenge is how to connect these two circuits together. After searching the Internet, I found several options, but all of them with additional call buttons. Or complex circuits on digital microcircuits. - individual mini-automatic telephone exchanges.

In simplified form, the telephone line is a constant current source with a voltage of about 60 V with an internal resistance of about 1000 ohms. When the call signal comes, it turns into an alternating voltage source of about 100V with the same internal resistance. That is, in principle, to "talk" you need to connect the telephones as in Figure 2.

But now there is a question after a challenge. In principle, it can be solved even in such a scheme, especially with some simple models of telephone sets equipped with electronic calls. Remember what happens if you pick up the receiver of one of the parallel telephones - the call of the second device will ring or squeak. And if you start dialing a number, then this ringing or beeping will continue all the time while the number is being dialed. So, here's your call signal. - pick up the phone and dial "O". The second apparatus will ring ten times.

Intercom for 2 subscribers with your own hands

There is also a drawback, firstly, not all telephones behave this way - it depends on the design of a particular ringing device. Secondly. even if there is a sound, it is not

It turns out that for a full-fledged call, an alternating voltage source is needed. The easiest way to apply AC voltage is through a separate wire. This is not a big problem, because now it is easy to buy a three-wire cable - it is used for wiring with grounding and is sold in any electrical goods store. In addition, his wires are multi-colored, which does not allow confusion when connected.

It turns out the circuit shown in Figure 3. The power supply is a ready-made transformer T1 with an output voltage of 42V. The voltage through the rectifier on the VD2 diode is fed to the capacitor C1. Where a constant voltage of about 60V is generated. It is fed through the VD1 diode and the R1 resistor to the TA1 and TA2 telephones.

The alternating voltage is removed before the rectifier and supplied to the telephones through the push-buttons S1 and S2. If we press on S1, the alternating voltage is supplied to TA2, which is in the state of a hung up tube, and therefore calls. If we press S2, the alternating voltage is now supplied to TA2, which is in the state of a hung up tube and is ringing.

Thus, to call the TA2 subscriber, the TA1 subscriber presses the S1 button, releases it and listens to the answer. To call the TA1 subscriber, the TA2 subscriber does the same, but presses the S2 button. The S1 and S2 buttons can be installed in telephone cases - there is usually a lot of free space. The transformer T1 is ready, you can use any transformer with a secondary voltage from 36 to 50V. The transformer can be even the smallest. - load current in this circuit is not more than 50 mA.

A simple scheme for connecting two old telephone sets for organizing a two-way communication line. It turned out that after the exchange of an apartment, two simple dial telephone sets became redundant. The new apartment did not have a telephone point, and no one regretted it - everyone had a cell phone.

The devices remained in the closet for several years, until it became necessary to organize two-way communication between the garage and the country house (both objects are on the same site).

Schematic diagram

And so, a diagram of a typical telephone set is shown in Figure 1. B1 and M1 are the components of the handset - an angle microphone and an electromagnetic capsule. F1 - call. S1, S2 - dialer, as long as it is not touched S1 is closed and S2 is open.

And when the number is dialed, S2 closes, and S1 opens the circuit as many times as the number of units of the dialed digit, for example, turned "9" - opened the line nine times. S3 is a rocker switch.

Rice. 1. Schematic diagram of a typical telephone set.

When the receiver hangs up, it is in such a position as in the diagram, that is, it connects the bell to the line. And when we pick up the receiver instead of ringing, he connects the receiver. The challenge is how to connect these two circuits together.

After searching the Internet, I found several options, but all of them with additional call buttons. Or complex circuits on digital microcircuits - individual mini-automatic telephone exchanges.

In simplified form, the telephone line is a constant current source with a voltage of about 60 V with an internal resistance of about 1000 ohms.

When the call signal comes, it turns into an alternating voltage source of about 100V with the same internal resistance. That is, in principle, to "talk" you need to connect the telephones as in Figure 2.

Rice. 2. The simplest scheme for connecting two telephones.

But now there is a question after a challenge. In principle, it can be solved even in such a scheme, especially with some simple models of telephone sets equipped with electronic calls. Remember what happens if you pick up the receiver of one of the parallel telephones - the call of the second device will ring or squeak.

And if you start dialing a number, then this ringing or beeping will continue all the time while the number is being dialed. So, here's a call signal - pick up the phone and dial "0". The second apparatus will ring ten times. There is also a drawback, firstly, not all telephones behave this way - it depends on the design of a particular ringing device.

Secondly, even if there is sound, it is not as loud as a regular call. It turns out that for a full-fledged call you need an alternating voltage source.

The easiest way to apply AC voltage is through a separate wire. This is not a big problem, because now it is easy to buy a three-wire cable - it is used for wiring with grounding and is sold in any electrical goods store. In addition, his wires are multi-colored, which does not allow confusion when connected.

It turns out the circuit shown in Figure 3. The power supply is a ready-made transformer T1 with an output voltage of 42V. The voltage through the rectifier on the VD2 diode is fed to the capacitor C1.

Where a constant voltage of about 60V is formed. It goes through the diode VD1 and the resistor R1 to the telephones TA1 and TA2.

Rice. 3. Schematic diagram of the connection of telephone sets with the possibility of calling.

The alternating voltage is removed before the rectifier and supplied to the telephones through the push-buttons S1 and S2. If we press on S1, the alternating voltage is supplied to TA2, which is in the state of a hung up tube, and therefore rings.

If we press S2, the alternating voltage is now supplied to TA2, which is in the state of a hung up tube and is ringing. Thus, to call the TA2 subscriber, the TA1 subscriber presses the S1 button, releases it and listens to the answer. To call the TA1 subscriber, the TA2 subscriber does the same, but presses the S2 button.

Details and construction

The S1 and S2 buttons can be installed in telephone cases - there is usually a lot of free space. The transformer T1 is ready, you can use any transformer with a secondary voltage from 36 to 50V. The transformer can be even the smallest - the load current in this circuit is not more than 50 mA.

Content:

Sometimes situations arise when communication is required only between two apartments, garages, summer cottages and other objects for various purposes. In this case, the use of a telephone switch is impractical, so the problem can be solved by an intercom for two subscribers.

Such systems have a significant limitation on line resistance, reaching 1-2 kOhm. The used copper wire with a diameter of 0.5 mm provides a communication range over a distance from several tens to several hundred meters, and when using an amplifier - up to 5-10 km. If you increase the length of the lines or the cross-section of the wire, the inductance will begin to increase and the capacitance of the line will increase, which will cause significant attenuation during the transmission of signals.

Principle of operation

The main components of the intercom are two consoles installed at the facilities and a two-wire communication line connecting these consoles. Each console is a communication device with an amplifier and a dynamic head. The last element can be dual-use. During the transmission of messages, the dynamic head acts as a microphone, and in the process of reception it is used for its intended purpose - to convert an electrical signal of an audio frequency into sound.

In most intercoms, the signal amplified by the head goes from one device to the dynamic head of the other via a direct communication line. Due to the low resistance of the head, losses occur in the communication lines: the volume of the sound begins to fall as the distance increases. Therefore, the operation of these systems is limited by the distance, depending on the scheme used.

Losses on the line can be completely avoided if the output signal from one remote control is fed not to the dynamic head, but to the amplifier of another device, which has a much higher resistance. It is such a connection that allows you to bring the reception and transmission of a signal up to several kilometers, without any significant losses. A significant advantage of such intercoms is the ability to power it from a low voltage source.

Schematic diagram of two-way communication

The schematic diagram proposed for consideration includes two consoles A1 and A2 and two communication lines connecting the sockets of the XS1 and XS2 consoles to each other. Since the amplifiers of the consoles have the same circuits, only one of them will be considered - from the A1 device.

For the audio amplifier, transistors VT2, VT3 and VT4 were used. The negative feedback voltage is supplied from the VT4 collector to the VT2 base through the resistor R8. Feedback helps to stabilize the operating mode of the transistors and the gain of the stage. Its action reduces the distortion of the sound.

When the send-receive switch SB1 is in the closed position, the input signal from the communication line to the emitter circuit VT2 is carried out through C1. Due to the small capacitance of the capacitor C1, the characteristics of the head are equalized for use as a microphone. Capacitor C2 protects the amplifier input from high frequency interference, and resistor R2 maintains the component of the emitter current VT2 at a constant value.

The VT1 stage is an electronic switch that supplies voltage to the first amplifier stage. This key is located in the load circuit (R3) of the transistor VT2. In the above diagram, the SB1 switches are in standby mode, and in the closed position. At this time, the current consumption of the devices from the power source is very insignificant. Therefore, the consoles do not require separate power switches.

After pressing the SB1 button, the BA1 dynamic head is connected to the amplifier input. In this case, the wire connected to the XS2 socket will be connected to the amplifier output. Further, from G1, power is supplied through R10 to the amplifier input of the second apparatus along its own line. The transistor VT1 in the second panel is opened, the supply voltage is applied to VT2 and the amplifier of the second panel is turned on. Simultaneously, in the first panel, the amplifier is also turned on in connection with the opening of the transistor VT1 by the current flowing through the dynamic head BA1 along the base circuit. During a conversation, a voltage is amplified in front of the head, which is generated in its voice coil and enters the communication line through the capacitor C5. Further, the signal weakened in the communication line is amplified, after which it goes to the dynamic head.

Thus, when the SB1 button is pressed, both remotes are turned on simultaneously. However, in the transmitting apparatus, the amplifier acts as a microphone and its current consumption is only about 3.5 mA. In the receiving equipment, it performs its direct function, consuming approximately 100 mA at the loudest sound. The conversation between the subscribers is carried out alternately. The button is pressed after receiving a message and released after the end of the transmission.

The intercom circuit is simplified by the absence of a volume control in it. Therefore, in order to prevent significant sound distortion, certain rules must be followed. If the line is short, up to 2 km, then you should talk softly, keeping a distance of 40-50 cm to the remote control. In the case when the devices are located at a maximum distance of 5-10 km, it is recommended to talk loudly, keeping a distance of 10-20 cm from the remote control.

Installation of intercom

For the installation of amplifier parts, a one-sided foil textolite is used as a board. The installation itself can be carried out not only by printing, but also by the hinged method, when special copper pins are fixed on the board under the leads of the parts.

The console body is made of steel, 0.5 mm thick. The board is fastened to the rear wall of the case so that the switch button protrudes outward.

In order to finally mount the intercom for two subscribers, it is necessary to determine the locations of the XS1 and XS2 sockets. Instead, you can use the small-sized connector from the tape recorder. All that remains is to fix the dynamic head, install the power supply and check the operation of the device.

A simple intercom can be assembled from two subscriber loudspeakers. Its application can be different, in the country, in the house, in the apartment, etc. In some cases, the use of a radio channel or mobile communication is unjustified, and often not possible. Especially if you need constant round-the-clock communication. For this, this design has been developed. The main advantage of the intercom is that the loudspeakers BA1 and BA2 are both microphones and a loudspeaker. There are two options for manufacturing the device. In the first variant, only one amplifier is used.

The device consists of a pre-amplifier on VT1 and a power amplifier assembled on the IC K174UN7. Switching reception modes - transmission is carried out using the switch S1, the switch is available only for one subscriber, with which you can connect the loudspeakers in turn to the input or output of the amplifier. A simplified diagram of the second variant of the intercom is shown in the following figure.

In this case, amplifiers M and switches S are installed in each speaker. Switching from reception to transmission can be done by each subscriber. When the switch S is pressed, the loudspeaker is used as a microphone and is connected to the input of the preamplifier through the blocking capacitor C1. The preamplifier is assembled on a VT1 transistor. Variable resistor R1 determines the feedback level and sensitivity at the input of the stage. From the output of the preamplifier through a variable resistor R5, the signal is fed to a power amplifier assembled on a DA1 microcircuit.

The resistor R5 controls the output power. From the output of the amplifier, the signal enters the line and, through the released button S2, goes to the loudspeaker, which in this case is used for its intended purpose. It should be noted that the line can be either two-wire or single-wire, if grounding is used as the second wire. Grounding can be water pipes, heating pipes, or just a metal rod driven into the ground.

The intercom is powered from a network nine-volt power source or galvanic cells. A properly assembled device starts working immediately, if necessary, you can adjust the sensitivity using the resistor R1, and using the resistor R5, adjust the output power. I used miniature loudspeakers, in which the step-down transformers were removed, instead of the volume controls, buttons S1, 2 of the P2K type were installed without fixing. Author: Valery Ivanov.

Types of communication devices Commax

• Hands-free devices: central and subscriber consoles in desktop and wall design, with an external or built-in microphone. Depending on the actual needs in the catalog, you can choose both a relatively simple two-way system ("cashier-client"), and complexes for 10, 20, 30 or even 50 stations.
• Commax wireless intercoms are solutions that provide maximum flexibility and mobility of execution, as well as ease of installation at any facility. The assortment of the online store includes both desktop hands-free devices and wall solutions with or without a tube. It should be noted that most of these systems are easily scalable and can combine up to 100 subscribers without the need for additional configuration and installation when expanding. On the other hand, inexpensive duplex devices that are convenient to use as an audio intercom are always popular.
• Wired intercoms with a handset are a traditional solution that is affordable and easy to use. There are simple sets of two handsets and systems for more subscribers with a keypad that allows you to quickly connect to any other point.

This variety allows you to choose the best solution for any object. The most widely used Commax intercoms in Moscow are used to equip:

• multi-apartment and private residential buildings (as a traditional audio intercom);
• large enterprises (for communication between departments, workshops, departments, etc.);
• trade and shopping and entertainment establishments, supermarkets, shops (for speakerphone and announcements in the trading floor, for communication with a warehouse, etc.).

Why Commax?

Today, Commax (South Korea), founded in 1968, is one of the recognized world leaders in the production of intercoms, intercoms and other electronic equipment for video surveillance and access control. The brand's products are sold in more than 100 countries, with Commax playing a leading role in its market segment in most of them. Intercoms of this brand are distinguished by well-thought-out functionality, certified in UL and TUV systems, and reliability of performance is confirmed by many years of experience.

Interphone Commax in the catalog of the online store "Rossi"

The Rossi catalog is an opportunity to buy Commax intercoms in Moscow with a choice of the best solutions among dozens of unique options. On the pages of the online store and during a telephone consultation, you can order kits and additional elements of the system in any quantity, in strict accordance with the characteristics of the object and the task at hand. Call now!