In general, the topic itself is not new, but browsing amateur and professional sites dedicated to communication technology has shown that interest in this topic is not waning. Such gadgets are produced by separate commercial offices, but for some reason their products are distributed mainly through online stores, and the prices are quite high. Adapters are sold with digital voice recorders for recording telephone conversations, but they become useless if you are the “happy” owner of a paired number - telephone polling pulses are not filtered by the standard adapter and are perceived by the microphone input of the voice recorder. As a result, the activation function of the record sound signal does not work - the voice recorder is always on, regardless of whether the handset is off the device or put down. Meanwhile, it is not at all difficult to make a high-quality adapter that takes into account the realities of the domestic telephone network. The adapter will help to record the necessary call with important information on a voice recorder (tape recorder, computer).

I tried to "fix" various circuit solutions that I came across on the Internet and in the literature. Figure 1 shows a conditional classification of adapters by type and, accordingly, by application with various recording devices:

The most convenient, of course, is a parallel connection to a telephone line. But, such an implementation imposes certain technical requirements on the circuit and its elements - the adapter is the load of the PBX line. Figure 2.1 shows the possible connection points for the adapter in parallel with the PBX line.
Inclusion of the adapter into the gap of one of the line wires, of course, simplifies the circuit design, but then the telephone line will have to be broken, and the place of the break must be “calculated” depending on which section of the line it is necessary to control the telephone sets. Such adapters are more suitable for working with an individual phone and are usually located near it. Figure 2.2 shows examples of connecting a line wire to a break. To make a record from all telephones, the line wire is broken at the beginning of the telephone wiring. In the figure, this is a special socket for the adapter, and the adapter must be constantly connected to it. If the adapter is disconnected, then a plug with a jumper is inserted into the socket instead, otherwise the telephone connection stops working in the entire room.
Adapters without galvanic isolation from the telephone line are used with battery-powered recorders and (or) receiving external power from a conventional transformer source with a stabilizer.
For recorders powered by pulse source(e.g. computers, digital voice recorders with battery charging via USB), galvanically isolated adapters are required. This, firstly, will ensure the safe operation of the device itself, and secondly, it will not affect the telephone line in terms of "ground leakage". As you know, the positive pole of the central battery at the telephone exchange is always grounded.
Non-power-management adapters are easy to connect to the recorder - communication is only through an audio cable. As they say, "Plug and Play" - plug and play. But, with such adapters, only voice recorders can work for a long time. Only voice recorders have a voice activation function (beep). The use of conventional cassette recorders for long work, with a standby mode, will not work, they do not have a voice control function in recording mode. Therefore, tape recorders with such an adapter can only be used for local recording - turning on at the beginning of a conversation and turning off at the end.
Another thing is the adapters that control the power of the recording device. When you pick up the handset from the unit, the device is in recording mode, power is supplied and it is activated. Standby mode can continue indefinitely while on-hook, with the battery or AC power completely turned off. Here, by the way, the problem of the operation of the recording device on the paired PBX line is automatically solved.
Using the telephone line power adapter to operate is classic version regardless of other types of circuit design. Here, both transformer binding to the line and capacitor can be used. But these are the simplest solutions. To expand the functionality of the adapter will allow additional power, which is convenient to use as an external power source for the recording device.
By implementing the types listed above in the necessary combinations, it is possible to manufacture an adapter circuit that fully meets a specific application.
On sale are unbreakable RTSHK kits - telephone sockets with a plug or various adapters that allow you to connect imported phones with a Jack RJ-11 plug to a domestic socket. Such kits or adapters are very convenient to use as an adapter case:

An example of the simplest adapters included in the break of any linear wire is shown in Figure 3:

A test and breadboard version of these adapters is shown in the photo:

In the circuit in Figure 3.1, a diode bridge VD1 is included in the break of the linear wire, the load of which is a fritter built on two germanium diodes connected in anti-parallel. The voltage drop across VD2 and VD3 is no more than 200…300mV both for an incoming call and when the line is busy. A capacitor C2 is connected to the fritter, which produces an alternating conversational current. For alternating current, capacitors C2 and C3 are a capacitive divider and form a kind of filter. From capacitor C3, an alternating signal from the line is fed to the microphone input of the cassette recorder. Capacitor C1 additionally shunts the input circuit of the adapter. It eliminates noise on the telephone line when the handset is on-hook and reduces the effect of AC calling voltage. The operating voltage of the capacitor must be at least as indicated in the diagram. In this circuit, you can install a line occupation indicator if, instead of VD2 and VD3, you turn on the LED with the anode to the plus of VD1. The constant voltage will then be limited to the level of the voltage drop of the type of LED used.
In the circuit in Figure 3.2, two silicon diodes VD1 and VD2 and the primary winding of the transformer T1 are included in the break of the linear wire. The voltage drop across the diodes does not exceed 600 ... 700mV both during an incoming call and when dialing a number, therefore, the diodes limit the voltage amplitude of the primary winding T1 at a safe level. From the secondary winding T1, the signal is fed to the tuning resistor R1, the engine of which can be set required level AC signal at the microphone input of the voice recorder. Capacitor C2 is separating. It is necessary if the microphone input of the recorder in the recording mode is "on duty" constant pressure(usually 0.9 ... 1.5V), which is used to power the connected external electret microphone. Capacitor C1 additionally eliminates interference. Any transformer T1 can be used, as small as possible, with a transformation ratio Ktr = 1 ... 10 and is selected experimentally according to the nominal level of the recorded signal.
Another version of the circuit design of the adapter included in the line wire break is shown in Figure 4. Here, the adapter uses a relay:

Figure 4.1 shows the diagram of the adapter that controls the voice recorder's power supply. In the initial state, when the handset is laid down, a voltage is applied to the VD1 diode bridge, determined by the current that the telephone set consumes from the PBX line in the last dialed number storage mode, if it is an electronic SLT with push-button dialing. No voltage is applied to the VD1 bridge if it is a classic rotary dialer SLT. The adapter is connected in series with the TA bell circuit. When an incoming call is received - an alternating voltage with an amplitude of 90 ... 120V, the phone starts ringing, while the ringing voltage is rectified by the VD1 bridge. Through the LED HL1, windings K1 and K2, the circuit closes to minus VD1. The HL1 LED indicates the presence of a ringing signal on the line. But, the phone's calling circuit current, sufficient to ignite HL1, is not enough to create a voltage drop across the resistance of the relay windings so that they work. Therefore, the relays remain in their original state, their contacts K1.1 and K2.1 do not switch, and as a result, the recorder is not activated. When the handset is removed from the device, the line is busy and a current begins to flow through the adapter, sufficient to ignite HL1 and operate the relay. Contacts K1.1 switch, closing the power supply circuit of the recorder, and contacts K2.1 connect the decoupling C3 to the plus VD1. The voice recorder records the conversation. When the handset returns to the device, the circuit assumes its initial state - the voice recorder is powered by the open contacts K1.1, and the decoupling C3 is closed to a common wire by contacts K2.1, i.e. recording stops. Capacitor C1 is storage and gives off its energy when the number is dialed, ensuring that the relay is kept on. Without it, the relays will switch with the dialing frequency (standard F=10Hz). The HL1 LED, in addition to the function of the incoming call indicator and the line occupation, blocks the shunting effect of the capacitor C1 on the alternating conversational current. Capacitor C2 - anti-interference. Diodes VD2 and VD3 eliminate negative self-induction voltage surges that occur when the relay is released. Recommendations for the use of the relay are given in the diagram, while we must not forget that the winding resistances K1 and K2 are connected in series with the conversational TA circuit and work as an additional resistance when dialing a number. Therefore, the lower their resistance, the better. According to this scheme, a working copy of the adapter was assembled, which fit in a socket with two RJ-11 connectors:

Contacts K1.1 operating in the power supply circuit of the recorder can be connected as follows. An insert is made of a thin but solid non-conductive material, which is placed between the battery and the contact in the voice recorder case. If this insert is used for one battery, then it is made according to the size of the battery diameter and has two contacts on different sides:

If this is an insert for two batteries, then it can be made rectangular:

In both cases, in the battery cover for the wire going from the insert to the adapter, you need to make a small neat cut with a needle file. Then it will turn out quite aesthetically:

In order not to pull the wire out of the battery compartment every time you listen to a recorded fragment, the adapter has a SA1 switch (see Figure 4.1). Closed contacts SA1.1 are included in the audio circuit, and open contacts SA1.2 are included in the power circuit. Before listening to the recording, SA1 is switched, then the power circuit is closed, and the audio signal circuit, on the contrary, is opened. Now you can control the voice recorder using its regular buttons, and the sound signal will not be sent to the microphone input if it becomes necessary to have a telephone conversation.
This adapter can not only control the power of the voice recorder:

But, also be used without power management, ie. in beep activation mode:

Figure 4.2 shows a simplified version of such an adapter - without voice recorder power management. Both schemes are perfect option for work on the coupled line of automatic telephone exchange.
Examples of adapters connected in parallel to a telephone line are shown in Figure 5:

Adapter, control external power supply voice recorder, shown in Figure 5.1. Here, an SA1 switch is installed at the input, connecting the adapter to ATC1 or to ATC2. The diode bridge VD1 ensures the constancy of the polarity of the supply voltage in the circuit and rectifies AC voltage call. Divider R1-R2 and transistor VT1 - line status sensor “busy; not busy; dialing a number". Elements R3 and C1 are the delay circuit, and VT2 is the current switch that controls the power of the recorder. As can be seen from the diagram, the switching of the voice recorder supply voltage is carried out "by minus". In the initial state, with the tube laid, the line is not busy and there is a voltage of the order of 2.0 ... 2.3V at the VT1 gate. The transistor is open and the voltage potential on the positive plate of the capacitor C1 is practically zero, i.e. C1 is discharged, and the transistor VT2 is closed. The circuit "minus source GB1-GB2" - "minus external power supply" of the recorder is broken. The current consumption from the line by the adapter circuit in this case is determined by the parallel connection of the resistances (R1 + R2) and R3, i.e. no more than 40 µA. When the tube is removed, the voltage at the gate VT1 becomes less than Uz-and the threshold and the transistor closes. C1 starts to charge through R3 and when the voltage on it exceeds the Uz threshold, the transistor VT2 opens, closing the negative wire of the external power supply of the recorder with the minus of the GB1-GB2 source. The recorder turns on and records the audio signal from the line, emitted by the capacitor C2 through R4. Capacitor C3 eliminates noise and interference. The voltage on the capacitor C1 will increase until it becomes equal to the voltage in the busy line (as a rule, U = 8 ... 15V and is determined by the subscriber device), therefore, it will not exceed Uz-and max VT2. The diagram shows the voltages measured when removing the tube from the push-button SLT of the brand "GE", taking into account the input resistance of the digital multimeter. When dialing a number, pulses with an amplitude of up to 60V appear on the line. At the VT1 gate, the voltage will reach Uz-and threshold and it will open again, instantly discharging C1. Transistor VT2 will close, de-energizing the recorder. During the repetition of serial pulses and in the pauses between them, C1 will not have time to charge, periodically discharging through a low resistance (Rc-and open = no more than 10 Om) of the drain-source transition VT1, so VT2 will remain closed and the recorder turned off. After dialing the entire number, C1 will charge and the recorder will continue recording. With an incoming call, the picture is similar to the dialing mode, so the voice recorder also remains off. The table shows instances of transistors that were tried as VT2, as well as the measured voltage drop (+ Upad *) at the open drain-source junction with "fresh" batteries GB1 and GB2. The use of IRFZ44N turned out to be more preferable - the voltage drop was no more than Upad = 4.0 mV.
The adapter according to this scheme was assembled in an arbacom socket with RJ-11 connectors due to its increased size, which made it possible to place a case for two AAA batteries, having previously cut a hole in the bottom to size:

The diagram in Figure 5.2 shows a non-power-managed adapter with the audio output closed in standby mode. The node on transistors VT1 and VT2 works in the same way as in the circuit in Figure 5.1, while the voltage U = 60V of the idle PBX line from the bridge VD1 through R4 goes to the zener diode VD4 and is limited at the level Ustab = 8 ... 10V. Capacitor C2 smooths out the ripples. The voltage from the cathode VD4 is supplied to the gate VT3 and opens it. With its open drain-source junction, the transistor connects the left side of capacitor C3 to a common wire. As a result, a capacitor with a capacitance C = 330nF + 1mF is connected in parallel with the microphone input of the recorder, which cuts off interference and shunts the alternating voltage of the incoming call, which, thanks to the divider R5 and Rc-and open VT3, is reduced to the noise level. The current consumption of the adapter is determined by the parallel connection of resistors R1 + R2, R3, R5 and the current flowing through R4 and VD4. When the tube is removed from the device, the transistor VT2 opens and discharges C2, while the gate VT3 closes to a common wire. Transistor VT3 closes and an alternating signal through R5 and C3 is fed to the microphone input of the recorder. When dialing a number, transistor VT2 will quickly close, but due to the large value of R4, capacitor C2 will not charge immediately, so VT3 will remain closed for some time. To prevent pulses with an amplitude of up to U = 60V from passing to the microphone input, a protective silicon diode VD2 is installed, which limits the voltage at a level of no more than 600 ... 700mV. In this case, R5 limits the current through the diode. Despite the high ratings of R5 and C4, the level at the microphone input is sufficient for the normal operation of the recording activation mode by a sound signal. You can increase the signal level by adding diodes in series with VD2.
Figure 5.3 shows the adapter circuit with galvanic isolation. The HL1 LED is included in the drain circuit of the transistor VT2, which is an indicator of line occupation. When the tube is removed from the SLT, resistor R4 eliminates the shunting of the line by the adapter and limits the current through the LED. The voltage drop on the LED (of the order of 1.5 ... 2.0 ... 3.0V and is determined by the type) is used to remove the signal from the line. Alternating conversational current through C2 is supplied to the winding 1-2 of the transformer T1. From the winding 3-4, the signal through the separating C3 is fed to the microphone input of the recorder. Capacitor C4 is anti-interference and reduces the amplitude of the induced voltage during an incoming call in winding 3-4 at the microphone input to a level at which the voice recording activation system does not recognize the signal. Such pickup occurs despite the fact that the transistor VT2 is closed and the cathode HL1, together with the output 2T1, is disconnected from the common wire of the circuit. The type of transformer T1 is not known and it is not clear whether it is unified or not. I found some at work and it is not clear what they are for or in what device they are used. They have small dimensions. The measured winding resistances are shown in the diagram, although they are not critical - the recorder has a deep ARUZ in the recording mode.
Based on the diagram in Figure 5.3, a two-line adapter circuit has been developed. I use this adapter at my work. The fact is that I have two phones connected at my workplace. One is a regular PBX with a serial number, and the second is a direct connection with the head of the department, i.e. the phone works with the operational communication switch. Previously, when telephone operatives or meetings were held, you had to press the receiver with your shoulder to your ear and manage to write down all sorts of control centers of bosses or technical managers. Tired, so this adapter was made. Now I calmly talk on the phone, and all the information is automatically recorded on the recorder.
Diagrams of two-line adapters connected in parallel with the telephone line and controlling the external power supply of the recorder are shown in Figure 6. Figure 6.1 shows a diagram of a two-line adapter with an additional option, and Figure 6.2 shows a simplified version:

As you can see from Figure 6.1, the adapter has two channels of telephone interfaces made according to the same schemes. The channels are interconnected only by the secondary windings of the transformers T1 and T2. This achieves galvanic isolation between telephone lines. The signal in the channels is taken through separating capacitors C3 and C4 from the LEDs HL1 and HL2, which simultaneously act as indicators of the occupation of telephone lines. In addition, emitting LEDs of transistor optocouplers VQ1.1 and VQ1.2 are installed in the drain circuit of transistors VT3 and VT4. transmitting a signal to the external power control node. Resistors R7 and R8 limit current and eliminate off-hook phone line shunting. The DD1 chip operates in the power management node - four logical elements with the "AND" function and a hysteresis switching characteristic. As an additional option of a voice marker that marks the time of completion (or start and end) of the fragment recording, a talking clock "TALKING CLOCK" has been added to the node.
The work of both telephone channels is the same, so I will consider the work of only one, for example, the first one. When the tube is laid, the transistor VT3 is closed, so the current does not flow through the LEDs VQ1.1 and HL1. Resistor R14 sets log.1-tsu at the inputs 1,2DD1.1, therefore, log.0 is present at the output 3DD1.1 . Log.1 from the output 10DD1.3 through the integrating circuit R17-C13 enters the input 6DD1.4. The input 5DD1.4 is also log.1, so the output 4DD1.4 is log.0. This log.0 closes the transistor VT7. Transistor VT6 is securely locked with a positive potential on the base with resistor R12, so the supply voltage from the source GB1-GB3 is not supplied to the recorder. Log.1-tsey output 11DD1.2 closed transistor VT5 and LED HL3 off.
The incoming call does not trigger any processes in the power management node, so the recorder remains turned off.
When you remove the handset from the device, the line is busy. VT3 opens and current begins to flow through VQ1.1 and HL1. The HL1 LED indicates the occupation of the line, and the phototransistor VQ1.3 opens in the optocoupler. At the inputs 1.2 DD1.1, the voltage drops to the level of log.0-la. Now, at the inputs 8 and 9 of the DD1.3 element, there are two log.1s, and at its output 10DD1.3, respectively, log.0. This log.0 quickly discharges C12 thanks to the VD5 diode and also quickly discharges C13 thanks to the VD6 diode. From the 4DD1.4 output, log.1 opens VT7, which, through the limiting current R13, connects the VT6 base to the common wire of the circuit. Transistor VT6 opens and power source GB1-GB3 through the emitter-collector junction VT6 and diode VD3 is supplied to the recorder. The recorder, previously included in the recording mode, starts recording the signal from the secondary winding T1. The signal from T1 is fed to the microphone input through the separator C5.
When laying the tube on the device, the phototransistor VQ1.3 closes and a log.0 appears at the output 3DD1.1 with a short delay, determined by the elements R14 and C10. Element DD1.3 inverts this log.0 and log.1 appears at the output 10DD1.3, coming through the discharged C12 to the "TALK" clock input. This is equivalent to pressing the standard clock button of the same name. The clock reports the time, and a PWM signal appears at the outputs out1 and out2 with the amplitude of the clock power supply, i.e. U=3V. At the same time, log.1 from the output 10DD1.3 through R17 will start charging C13, so log.1 at the output 4DD1.4 will be held for some time, sufficient to start the clock and the recorder will not turn off even for a short time. Further, after charging C13, the on state of the recorder keeps the PWM signal from the output out1 of the clock, constantly recharging C11 through VD4 and R15. A voltage with a log.0 level from the output 11DD1.2 through R10 opens VT5 and the HL3 LED indicates the process of recording a time message to the recorder. The PWM signal to the recorder comes through R11 and C9. After the time message is over, log.0 will appear at the 4DD1.4 output, closing VT7 and VT6, and the recorder will be powered off.
If you pick up the handset not to answer an incoming call, but to call yourself and start dialing, then the dialing pulses in the line will close VT3, therefore, the power management circuit will work out as when laying the handset. Therefore, the clock will also tell the time and the recorder will record a voice marker. Thus, when you answer an incoming call, the time message will be recorded at the end of the conversation, and when you dial out, the time message will be recorded both at the beginning of the conversation and at the end.
The dictaphone circuit was placed in a case from a used musical apartment bell “Door bell” with battery power and corridor lighting:

At the watch, “holders” for the strap were ground off with a needle file, and a hole for the watch was cut in the bell case. After that, the clock was glued with glue "second":

Inside the case, two telephone jacks were placed and a board was cut to size:

In Figure 6.1, a fragment of the circuit is highlighted in blue. This is a PWM signal amplifier for the BF1 dynamic capsule. When the build was nearing completion, the amplifier was added to the circuit. The measured resistance of BF1 is R = 140 Om (a telephone capsule from a dead cell is used), so the sound is not loud. Let him purr. Capacitor C8 allows you to record a voice marker if the adapter is used with a voice recorder without power management. If there is no need to record a voice marker, then C8 can be omitted. Diode VD3 reduces the supply voltage to the recommended U=3.6V. At the collector-emitter junction of the VT6 transistor with this model of the recorder and “fresh” batteries, no more than U = 0.33V drops.
In the circuit in Figure 6.2, phototransistors VQ1.3 and VQ1.4 are included in the gate circuit of the KP505A transistor switch. When the phototransistors are closed, the zero potential on the gate sets the resistor R=560K. Power switching in the circuit is carried out "by minus".
The topic is invited to watch demos. Trial calls were made to the telephone informant of the city cinema. The first video shows a recording of the conversation on a voice recorder, and the second - on a laptop. For testing, a simple program for recording from a microphone input was downloaded from the Internet. Naturally, there are more "advanced" programs, for example, automatically start recording when there is a signal at the input of the sound card.

RECORDING A TELEPHONE CONVERSATION ON A DICTOPHONE

RECORDING A TELEPHONE CONVERSATION ON A LAPTOP

Many people wonder - why do we need special devices that record conversations from landline phones? This is necessary in order to ensure security and privacy. various information. For some offices and various companies, this is a very necessary device that can easily determine the culprit of leaks of various information that should not be distributed in any case and under no circumstances.

Therefore, many firms, for security reasons, install special devices for recording telephone conversations, and this recording can be used as evidence in court or to fire a person who has made a mistake. Previously, when these devices did not yet exist, it was possible to use a personal computer that has a Dial-Up modem. By connecting a telephone cable to the modem and installing a special software, you can intercept a telephone conversation from one line, listen to everything that is said on the phone or make a recording, including setting the program so that it starts recording when the handset on the other end goes up.

But now, in this moment When the technology industry is heading up, you can find special devices on the market that automatically intercept telephone conversations and save it on your computer. There is no longer a need to buy multiple modems for multiple telephone lines - now there are special boxes for several ports, which simplifies the task.

If you are interested in these devices, then you can purchase them in special stores where special devices are sold that ensure confidentiality, security and safety of various information. By purchasing this device, you can at any time make recording of telephone conversations. For a company this is a very necessary and useful equipment that will allow you to record and listen to various telephone conversations and identify the perpetrator of the leak of confidential information.

However, everyone can use this device at their own discretion. Some people buy these models just to record digital information that they can listen to and think about the whole conversation. Prices for such devices vary from four thousand rubles and more, depending on the number of incoming telephone ports.

The described device automatically turns on the tape recorder to record the conversation and turns it off when the handset is hung up. When using the set-top box, the tape recorder must be constantly turned on for recording. Switching on and off occurs by switching the power circuit. The attachment diagram is shown in fig. 1.

The telephone line voltage is applied to the Divider across resistors R1 and R2. When the tube lies on the lever, the voltage in the line is about 60 V, at the output of the element DD1.1 low level, the capacitor C1 is discharged, the output DD1.3 is also low, the transistor VT1 is closed, the relay K1 is de-energized, the power of the tape recorder is turned off. When the tube is removed, the voltage in the line drops to 5 ... 12 V, at the output DD1.1 - high level, the capacitor C1 begins to charge through the resistor R3.

When the threshold level is reached at the terminals of the capacitor, the state of the elements DD1.2 and DD1.3 changes to the opposite, as a result of which a high level appears at the output of DD1.3. Transistor VT1 opens, relay K1 is activated. Through the closing contacts of the relay, power is supplied to the tape recorder. Voltage audio frequency from the line is fed through the circuit SZ, C4, VD4, VD5, C5 to the line input of the tape recorder.

Rice. 1 circuit diagram set-top boxes for automatic recording of telephone conversations

At the end of the conversation, as soon as the handset is placed on the lever, the voltage in the line rises to 60 V. A low level appears at the output of the DD1.1 element.

Capacitor C1 starts to discharge through resistor R3 and element DD1.1. As soon as the voltage on the capacitor reaches the threshold level, the elements DD1.2 and DD1.3 will change their state to the opposite. Transistor VT1 will close, relay contacts K1 will open and turn off the power of the tape recorder. Since the time constant of the R3C1 circuit is significantly more period following a series of "dialing" pulses when picking up the handset and dialing a number, the tape recorder remains de-energized. However, if you pick up the phone and do not dial the number for a while, the capacitor C1 will have time to charge and the tape recorder will turn on.

Sending a call signal (80 ... 120 V, 25 Hz) also does not change the state of the elements DD1.2 and DD1.3. Diode VD2 limits the voltage at the input of the element DD1.1. The resistance of capacitors C3, C4 at a frequency of 25 Hz is over 60 kOhm each, so they do not shunt the ringing signal. Diodes VD4, VD5 limit the voltage at the input of the tape recorder at the level of 0.6 ... 0.7 V.
The K561LA7 chip is interchangeable with the K561LE5, as well as with the similar K176 and K564 series. The diode assembly KTS407 can be replaced by four diodes with a permissible reverse voltage of more than 200 V. Transistor VT1 - structures n-p-p with a permissible collector dissipation power of at least 150 mW. Relay K1 - for a response voltage of 5 ... 7 V, for example, RES 10 (passport RS4.524.302 or 031-04-02), RES15 (passport RS4.591.003).

Establishing the device is reduced to the selection of R1 and R2 to ensure a clear operation of the DD1.1 element when removing and lowering the tube. The resistance of the resistor R1 should not be less than 330 kOhm.

In various dispatch services, in the offices of enterprises, and in some domestic cases, it may be necessary to record telephone conversations. Of course, there are various digital "recorders" now, but this is equipment that needs to be specially purchased. Despite the fact that almost any morally obsolete and no longer in use cassette tape recorder capable of recording an audio signal, at least with mediocre quality, can be adapted to record telephone conversations.

How to record a telephone conversation

The site shows a diagram of a matching device that provides automatic recording of telephone conversations on a cassette recorder. The circuit is connected to a telephone line in any of its places and can record conversations from any number of parallel telephones. The recording device, as mentioned above, is any workable cassette tape recorder. From this circuit, an audio signal is supplied to it, as well as the contacts of relay K1 are included in the break in the power circuit of the motor of the tape drive mechanism of the tape recorder.

If there is a source in the tape recorder circuit direct current voltage 9V, this circuit can be powered from it. Otherwise, from any separate 912V current source.
The system operates as follows. You need to connect the system to the telephone line, turn on the tape recorder for recording (turn on its power, press the "record" or "record" button).

Since the power of the tape recorder's CVL motor will be turned off, recording will not occur. When you pick up the handset on any of the telephones connected to this line, the contacts of relay K1 will close and recording will begin. Important point if the tape recorder has an autostop that does not allow the mechanism to be stationary for a long time, it must be turned off or dismantled.

Now about the work of the scheme. When the line is not busy it has a relatively high DC voltage (usually over 40V). The stabilization voltage of the zener diode VD7 is much lower (12V), so its reverse resistance decreases and through it and the resistor R3 a certain constant voltage is supplied to the base of the transistor VT1, at which the transistor VT1 opens. In this case, the voltage at the collector VT1 is low and the transistor VT2 is closed. The current does not flow through the relay winding, its contacts are open and power is not supplied to the electric motor of the tape recorder.

When lifting the handset, the voltage in the line drops to 5-10V, sometimes lower (depending on the telephone set). This is lower than the stabilization voltage of the VD7 zener diode, so the current through it stops. The voltage at the base of VT1 gradually drops as the capacitor C2 is discharged, as a result, the transistor VT1 closes. But at the same time, the transistor VT2 opens, because the voltage at its base increases. Current flows through the winding of the relay K1 and its contacts turn on the power supply of the VLM motor of the tape recorder. Recording starts.

After the end of the telephone conversation, the voltage in the line rises again and the power supply of the LPM electric motor is turned off. The audio signal to be fed to the recording path of the tape recorder is formed by the C1R1 VD5VD6 circuit. C1 decoupling capacitor, resistor R1 and diodes VD5 and VD6 form a signal limiter. When adjusting, the resistance R5 should
choose the one in which the recording quality will be optimal.

Relay K1 old relay from remote control domestic TVs. It can be replaced by any other relay with a 12V winding with a resistance of at least 200 Ohm. Zener diode VD7 is any low-power zener diode for a stabilization voltage of at least 12V and not more than 35V. The remaining parts can be replaced by any available analogues.

The ICON TR1 telephone recorder is a fully autonomous device for recording telephone conversations over a 2-wire analog line.

The device does not require:

• connection to a computer- calls are recorded on a microSD card
• external power supply- the device is powered by a telephone line

The package includes a microSDHC card with a capacity of 16Gb, which allows you to record telephone conversations with a total duration of up to 1100 hours. The user can install a larger capacity card - the device supports microSDHC cards with a capacity of up to 32Gb (2200 hours of recording).

The recording of a telephone conversation is in WAV format. Each conversation is recorded in a separate file. When the card is full, new conversations are recorded over the oldest ones.

TR1 supports ANI in Russian format and in CallerID (FSK/DTMF) format.

The map maintains a log file in HTML format, in which the following are recorded:

• start time and duration of the call
• outgoing/incoming number
• link to the recording file

The user can view the log file and listen to recordings using any Internet browser.

User can write to microSD card sound file, which will be played on an incoming call before recording starts. This can be a greeting or a warning that the conversation is being recorded. Note:TR1 will play this file when the phone goes off-hook, so both parties will hear the message. If you want the device to answer the call itself, play the message to the caller, and then transfer the call to the connected phone, we recommend models TR1NT and TRX1AN.

The ICON TR1 telephone recorder is not intended for covert recording of telephone conversations.

The ICON TR1 telephone registrar is recommended to be used on city telephone lines with one connected telephone set. For cases when two or more parallel phones are connected to the line, as well as for use on PBX internal lines, GSM and VoIP gateways, etc. we recommend externally powered models ICON TR1NT and ICON TR1NS.

Characteristics: