Electrical circuits of wall telephones 1908. Repair of imported telephone sets. Scheme, description. Phone diagram main components
A simple diagram for connecting two old telephone sets to organize a two-way communication line. It turned out that after the exchange of an apartment, two simple rotary telephone sets became redundant. There was no telephone point in the new apartment, and no one regretted it - everyone had cell phones.
The devices remained in the storage room for several years, until it was necessary to organize two-way communication between the garage and the country house (both objects are on the same site).
Schematic diagram
And so, the diagram of a typical telephone set is shown in Figure 1. B1 and M1 are the components of the telephone handset - a carbon microphone and an electromagnetic capsule. F1 - call. S1, S2 - dialer until it is touched S1 is closed and S2 is open.
And when a number is dialed, S2 closes, and S1 opens the circuit as many times as there are units for the dialed digit, for example, turning “9” opens the line nine times. S3 is a lever switch.
Rice. 1. Schematic diagram of a typical telephone set.
When the receiver hangs in the position as in the diagram, that is, it connects a bell to the line. And when we pick up the phone, instead of calling, he connects the receiver. The challenge is how to connect these two circuits to each other.
After searching on the Internet, I found several options, but all of them with additional calling buttons. Or complex circuits on digital microcircuits - individual mini-PBXs.
In a simplified form, a telephone line is a direct current source with a voltage of about 60 V with an internal resistance of about 1000 Ohms.
When a call signal comes in, it turns into an alternating voltage source of about 100V with the same internal resistance. That is, in principle, in order to “talk” you need to connect telephone sets as in Figure 2.
Rice. 2. The simplest scheme connecting two telephone sets.
But now comes the challenge after the 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 handset of one of the parallel telephones - the bell of the second device will ring or squeak.
And if you start dialing a number, this ringing or beeping will continue the entire time the number is being dialed. So, here’s your call signal: pick up the handset and dial “0”. The second device will ring ten times. There is also a drawback, firstly, not all telephones behave this way - it depends on the design of the 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 call you need an AC voltage source.
The easiest way is to supply alternating voltage via a separate wire. This does not create a big problem, because now it is easy to buy a three-wire cable - it is used for electrical wiring with grounding and is sold in any electrical goods store. In addition, its wires are multi-colored, which prevents confusion when connecting.
The result is a circuit shown in Figure 3. The power source is a ready-made transformer T1 with an output voltage of 42V. The voltage through the rectifier on diode VD2 is supplied to capacitor C1.
Where a constant voltage of about 60V is generated. It is supplied through diode VD1 and resistor R1 to telephone sets TA1 and TA2.
Rice. 3. Schematic diagram of connecting telephone sets with calling capabilities.
The alternating voltage is removed before the rectifier and supplied to telephone sets through switch buttons S1 and S2. If we press S1, alternating voltage is supplied to TA2, which is in a hung-up state and therefore rings.
If we press S2, the alternating voltage is now supplied to TA2, which is on-hook and ringing. Thus, to call subscriber TA2, subscriber TA1 presses the S1 button, releases it and listens for the answer. To call subscriber TA1, subscriber TA2 does the same, but presses the S2 button.
Details and design
Buttons S1 and S2 can be installed in telephone cases - there is usually a lot of free space there. Transformer T1 is ready, you can use any transformer with a secondary voltage from 36 to 50V. The transformer can even be the lowest power - the load current in this circuit is no more than 50 mA.
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Phone diagram main components
1. CPU. It is usually designated on drawings as CPU or RAPIDO; RAP is the main brain of your mobile phone.
2. Flash drive This is the most common memory card, designated in service instructions by the word flash. The designations mem and memory are also found. It is usually rectangular in shape and can vary greatly in both dimensions and volume.
3. Power controller. It can be marked on mobile phone diagrams as betty, retu, tahvo or UEM. Outwardly, they look like small square microcircuits.
4. Also, among other things, any mobile phone contains transmitter and receiver RF chip & GSM FEM. Be very careful when replacing transmitters. Some may be similar in appearance, but differ in the last digits in the marking.
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Capacitive and resistive touch screen design |
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When the vibration alert on your phone stops working, it causes a lot of inconvenience. Vibrating alert is a very convenient phone function, which is not so easy to refuse if such a malfunction occurs. It is about solving the problem of vibrating alerts in a mobile phone that we will talk in this article.
In some life situations, you need to find out if there is an active mobile phone nearby, for example, during exams. Or notify a hard of hearing person about the arrival of an SMS. For these cases, we need a mobile phone ringing indicator. Such a detector can be easily assembled with your own hands based on a simple circuit, even with basic amateur radio skills.
For the telephone to operate, two conditions must be met: to provide power to the conversation circuits with a constant voltage of 1.5 - 9 volts (depending on the type of device) and to provide power to the call circuits with an alternating voltage of 40 - 60 volts, 25 - 50 Hz. Based on the power supply principle, telephone sets are divided into two groups. The first group includes local battery (MB) devices, in which all power sources are located inside: a galvanic battery for powering conversation circuits and a manual AC inductor for sending a call to the subscriber. Such telephones include field military devices TAI-43 and TA-57. The second group includes central battery (CB) devices, the circuits of which are powered from a central station or automatic telephone exchange; these devices do not have their own power sources. Such telephones include all devices with dialers and some other general use types: TA-68, TAN-70, VEF TA-12, Aster, etc. When the devices of the first group are connected to each other by a two-wire line, they immediately begin to work without any problems, since they are MB devices with a local battery. In order to make two interconnected devices of the central bank of the second group work, I assembled a special device. There are quite a few descriptions of such devices, but all of these schemes, as previously written, have a significant drawback - a three-wire line is required to connect the devices. The device I assembled provides operation over a two-wire line.The power supply itself is located on the side of one of the subscribers and consists of a step-down network transformer Tr1. The secondary winding of the transformer provides two voltages: 40 and 15 volts. An alternating voltage of 40 volts provides the calling circuits. The second voltage is rectified by the CC bridge and stabilized by a stabilizer on the ROLL - it is used to power the conversation circuits. The stabilizer and capacitor C1 are needed to reduce the background alternating voltage during a conversation. The stabilizer can be neglected if the background is not large. KN buttons are used without fixation and are mounted in telephone bodies. The TA2 device is connected to the TA1 device and the telephone device using a two-wire TRP 1 x 2 wire. The lower contacts of the switches KN1 and KN2 according to the diagram are grounded. Grounding can be a water supply pipe, heating pipe, or a metal pin driven into the ground. I used the ground contact of a Euro socket.
Operation of the circuit. When you press the KN1 button on the TA1 device, an alternating voltage of 40 V from the transformer winding through the closed contacts of the EH1 button is supplied through the line, the normally closed contacts of KN2 to the ringing device of the TA2 device. (when the handset is on the device, a ringing device is connected to the line). From the device through the line, capacitor C1, to the second horse winding 40 V. The phone TA2 rings. When the telephone handsets are lifted in both devices and the buttons KH1 and KH2 are pressed, the intercom circuits of the devices are connected to the line. In this case, the 12 volt DC power supply is connected in series with the telephone sets. By circuit: Capacitor C1 plus the power supply, connecting line, spoken circuits of the TA2 device, closed contacts of the KN2 button, line, closed contacts of KN1, spoken circuit of the TA1 device, minus the power supply. The scheme works similarly when sending a call from the TA2 telephone set. When the KN2 button is pressed, the ringing alternating voltage of 40 V from the transformer winding through the grounding and closed calling contacts of KN2 enters the line and through the contacts of KN1 to the telephone ringer TA1 and the second end of the 40 V winding Tr1. The conversation of subscribers takes place according to the circuit described above. In my use case of this device at the installation point of the TA2 telephone there were no lines at all except for the grounding and the cable television cable going to the TV. Laying a new line through the building was far away and expensive, and the television cable ran not far from the installation of the TA1 telephone. As a result, I was able to connect the TA1 and TA2 telephone sets using the already installed RK75 television cable without disturbing the operation of the TV. For these purposes, I installed special isolation filters on the cable.
Chokes Dr1 and Dr2 serve to suppress high-frequency television signals from penetrating phones and at the same time maintain the physical circuit between the devices. Wound on MLT 100 resistances with PEL 0.2 wire until filled. The screen braid of the RK75 cable is used as the second wire of the line. Capacitors C1 and C2 prevent voltage from penetrating elements of television equipment, but in turn they transmit radio frequency television signals well. Everything works stably.
A. Evseev
On the shelves of many stores you can find a wide variety of telephones. But they are a ready-made assembly of homemade communication devices, especially when there is no real telephone. In one case, it may be an intercom between two subscribers, in another, a more complex automatic machine for communication between ten subscribers through a central console, in a third, a miniature telephone exchange that provides automatic communication between subscribers, as with regular telephone communications.
Such devices will be discussed in the article. They can find application, for example, in schools, pioneer camps, collective and state farms. The communication range in all cases is limited by the line resistance - 1...2 kOhm, which when using a copper wire with a diameter of 0.5 mm is 5...10 km. It is prohibited to connect the described devices to the city or local telephone network.
Private translator of technical texts
Intercom
It provides telephone communication between two subscribers. The call is made through the bell available on the telephone. Moreover, the device can operate telephones that only have a working handset and bell.
Rice. 1. Diagram of the intercom
Telephone sets are connected by a three-wire line (Fig. 1), to which AC and DC voltages are supplied. The first is removed from winding II of the decoupling step-down transformer T1, the second is removed from the diode rectifier VD1, powered by winding III.
If, for example, the first subscriber (he has a TA-1 telephone set) wants to call the second subscriber, he must press the switch button S.B.1. In this case, alternating voltage from winding II of the transformer will be supplied to the TA-2 telephone set, and the bell will ring. When both devices are off-hook, the constant voltage source will be connected in series with the devices - you can carry on a conversation. The second subscriber, when calling the first, presses the switch button S.B.2.
The rectifier diode can be any of the D2 (except D2B), D7, D9 (except D9B), D226 series. Capacitor C1- K50-3, K50-6, EGC. Push-button switches - KM-1, P2K, power switch - TV2-1. The transformer is made on a strip magnetic core ШЛ16X25. Winding I contains 2200 turns of PEV-20.08 wire, winding II - 360 turns PEV-20.12, winding III - 100 turns PEV-2 0.21.
Telephone sets can be, for example, TA-68, TAN-66, TAN-70. If devices with faulty dialers are used, you should disconnect the conductors from the dialers and connect them to a lever switch so that when the handset is lowered, a bell is connected to the line through a 1 µF capacitor (it is in the device), and when the handset is raised, a series-connected microphone and handset telephone.
The transformer and rectifier parts are mounted in the housing of the TA-1 apparatus. A power switch is installed on its back wall, and a power cord with a plug at the end is brought out through a hole in the wall. Switches are installed on the bodies of the devices. For the line, use a single-core or multi-core telephone or installation wire with a core diameter of at least 0.5 mm for long distances (up to 1 km) and at least 0.2 mm for short distances (up to 200 m).
Rice. 2. Telephone exchange diagram
Telephone exchange with switch
As mentioned above, such a station with a central control panel - switchboard - is designed to connect ten telephone sets. Each subscriber can contact the person on duty at the central console, and through him -. with any other subscriber.
The schematic diagram of the station is shown in Fig. 2. It’s convenient to start getting acquainted with its work from the moment when you need to contact, for example, the first subscriber (the owner of the device) from the central console TA-1). In this case, the moving contacts of the switch S.A.1 move to the bottom position according to the diagram and press the switch button S.B.1 "Call". Alternating voltage from winding II of transformer T1 supplied through a diode bridge VD5 - VD8, Light-emitting diode H.L.11, closed switch contacts S.B.1 and group S.A.1.1 switch S.A.1, resistor R1 to a telephone set TA-1 - the bell rings in it. The LED that lights up indicates that the communication line is working properly and the call signal is going to the subscriber’s device! As soon as the subscriber picks up the phone, you can carry on a conversation (of course, the switch button S.B.1 already released). The conversational current passes through the circuit - the common wire of the power source - the telephone B.F.1 and microphone VM1 central console handset - normally closed switch contacts S.B.1 - closed group contacts S.A.1.1 - resistor R1 - telephone set TA-1- positive terminal of the power supply.
Let us now assume that the subscriber of the device TA-1 you need to call the central control officer on duty. To do this, he just needs to pick up the handset of the device, and the communication line will be connected through the resistance of the device and a resistor R1. To the base of the transistor VT1 positive voltage will be applied. The transistor will open and the warning light will light up H.L.1. At the same time, the photothyristor of the optocoupler will open, and alternating voltage from winding II of the transformer will be supplied through the diode bridge VD1 - VD4 to call HA1 The attendant will move the switch handle S.A.1 to the opposite position (compared to that shown in the diagram) and starts talking to the subscriber.
If the subscriber of the device TA-1 wants to contact, for example, the subscriber of the device TA-10, attendant using switches SAW And S.B.1 calls this subscriber. He picks up the phone, and the callers can carry on a conversation. True, the sound volume will be less than when talking with the duty officer.
As soon as any subscriber of this station picks up the handset of his telephone, either short or long sound signals (“beeps”) are heard, entering the lines through the emitter junctions of transistors VT1- - VT10 from a resistor divider R15, R16. The signals are generated by two generators. Frequency of the first generator assembled on logical elements DD21 - DD23 is 300...500 Hz, the frequency of the second (it is assembled on elements DD1.1 - DD1.3 and transistor VT11) - 0.3… 1.5 Hz. On a logical element DD1.4 the generator signals are summed up and sent from its output to the divider R15 R16.
When the moving contacts of the switches S.A.1 - SAW are in the initial position shown in the diagram, while the driving circuit of the second generator includes series-connected resistors R11 And R12. You can hear “long beeps” when you pick up the handset of any telephone. If the moving contacts of at least one of the switches are in the other extreme position (lower in the diagram), the resistor R11 closes and “short beeps” come into the line, indicating that the central control person on duty is talking to someone.
Rice. 3. Printed circuit board (A) telephone exchange and the location of parts on it (b)
Switch S.A.11 if necessary, turn off the call HAL Resistors Rl - R10 limit the base currents of transistors VT1 - VT10.
A unit with two stabilizers is used to power the telephone exchange. The first one is made on zener diodes VD10, VD11, ballast resistor R18 and regulating transistor VT12 and serves to power the speaking circuits of devices and call alarms. The second is made up of a ballast resistor R17 and zener diode VD9 and is necessary to power generators.
Transistors VT1 - VT11 - any of the KT312, KT315, KT603 series; VT12 (it is installed on a radiator with a surface area of at least 20 cm2) - any of the KT801, KT807, KT815, KT817 series. Optocoupler U1 - any of the AOU103 series. In the absence of an optocoupler, you can use a slightly different switching circuit given in the description of the telephone exchange in the article “Craftsmen of the Electron Club” in the magazine “Radio”, 1983, No. 3, p. 51. LED H.L.11 - series AL102, AL 112, AL307 with any letter index. Diodes VD1 - –VD8 - any of the D101, D102, D220, D223, D226 series; VD12 - VD15 - any of the D7, D226, KD209 series. Capacitors C1 - C5 - K50-3, K50-6, K50-12. Resistors - MLT-1 (R17) and MLT-0.25 (rest). Switches S.A.1 - SAW - TP1-2, switches S.A.11, Ql - TB2-1, push-button switch S.B.1 - KM1. Call HA1- from a telephone set, winding resistance 1...3 kOhm, designed to operate on alternating voltage.
Telephone B.F.1 and carbon microphone VM1 combined in a standard telephone handset.
Power transformer 77 is made on a strip magnetic core 1Sh116×25. Winding I contains 2200 turns of wire PEV-20.08, winding II - 360 turns PEV-20.12, winding III - 240 turns PEV-20.21.
Most of the elements of the telephone exchange are mounted on a printed circuit board made of foil fiberglass (Fig. 3). To connect the pins of the parts with the rest of the remote control circuits, you can provide mounting points on the board or install hollow rivets. The author solved this issue by installing a small-sized multi-pin connector MRN44-1. For this option, the numbering of the connector contacts is shown in the diagram as numbers with dashes.
Setting up a station comes down to selecting a resistor R14 at the required frequency (approximately 40Q Hz) of the audio signal, as well as resistors R11 And R12 according to the required duration of “beeps”.
Automatic telephone exchange
This design is more complex than the previous one, but also more advanced - calling a subscriber in it is carried out by dialing the corresponding number (from 0 to 9) using the telephone dial. As in a real PBX, the proposed home-made station provides duplex communication between any two subscribers, monitoring the progress of a call by listening to “long beeps” in the handset, signaling that PBX lines are busy (“short beeps” in the handset), installing a PBX in the initial state after the telephone handsets are placed on the devices.
In Fig. Figure 4 shows the block diagram of the automatic telephone exchange. Telephone sets are connected to a subscriber node, which houses electronic relays that provide communication between two subscribers and turn off other devices at this time. In the signal and control node, dialing pulses are generated (when the dialer rotates back), as well as line status signals - “continuous beep” when the line is free and “short beeps” when it is busy. In the dialing unit, the pulses received from the dialer of a particular device are counted and subscribers are connected. The power supply provides the telephone exchange with constant and alternating voltages.
Rice. 4. Block diagram of the automatic telephone exchange
Now let’s look at the operation of the automatic telephone exchange according to its principle diagram (Fig. 5). When the first subscriber (who owns the device) TA-1) wants to talk to, say, the tenth person, he picks up the phone. Through the device and normally closed contacts of the group K16.1 DC voltage is applied to the base circuit of the transistor VT6. After charging the capacitor C4 the transistor opens. The relay is activated K14 and contacts K 14.1 supplies power to relays K1 - K13, and the contacts K14.2 prepares the chip DD4 to work.
In addition, when the handset of the device is lifted TA-1 through it, resistor R1, normally closed group contacts K.16.1,K1 .1 and control electrode of the thyristor VS1 starts to leak D.C.. The thyristor opens, and the relay K1 included in its anode circuit is activated. The current flowing through the relay winding, and therefore the anode circuit of the thyristor, exceeds the holding current of the thyristor, and the thyristor will remain on even after the current through the control electrode stops (this will happen after the relay is triggered K1).
As soon as the moving contact of group K1.1 of relay K1 is connected to the bottom contact in the circuit, current will flow through the emitter junction of the transistor VT4. The transistor will open, the relay will operate K12. At the same time, in the handset of the device TA-1 the subscriber will hear a continuous sound signal with a frequency of about 400 Hz, indicating that the station is ready to dial the number of the called subscriber. This signal will be applied to the communication line through the emitter junction of the transistor VT4 and logic element DD2.2 from a generator assembled on logical elements DD1.1 - DDL3. At the same time contacts K12.1 relay K12 is connected via diodes VD1 - VD10 control electrodes of all thyristors with their cathodes. This prevents the SCRs from turning on VS2 - VS10 when picking up telephone handsets TL-2 - TA-10. If one of the handsets is picked up, the subscriber will hear intermittent signals (line busy) coming from the divider R15 R21. These signals are formed as a result of summation by the element DD2.3 signals with a frequency of 400 Hz from an element generator DD1.1 - DD1.3 and signals with a frequency of about 2 Hz from an element generator DD1.5, DD1.6 and transistor VT2.
Next, the first subscriber uses the dialer of his device to dial the number 0, that is, the number of the tenth subscriber. When the dialer rotates back, the current in the transistor base circuit VT4 will interrupt ten times and release the same number of times and the relay will operate K12 His contacts K12.2 together with an RS trigger on logical elements DD3.1 And DD3.2 will generate the corresponding number of pulses that will arrive at the counter DD4 The counter outputs are connected to the inputs of the decoder-demultiplexer DD6, converts BCD to decimal. If there are strobe inputs (pins 18 And 19} logical level 1 at all outputs of the decoder there will be a logical level 1.
Rice. 5. ATS scheme
If there is a logical level of 0 at the strobe junctions, a logical level of 0 will also appear at one of the outputs, and the number of this output will correspond to the decimal equivalent of the binary number written into the counter after dialing the number.
After the arrival of the first set pulse at the output of the microcircuit DD5 (it performs the 4OR-NOT operation) a logical level 0 appears. It is inverted by the element DD3.3, and from the output of the element, logical level 1 goes to one of the inputs of the logical element DD2.1. A logical level of 0 appears at the output of this element, which prohibits the supply of a continuous signal to the line of the first subscriber (“the long beep” stops). Simultaneously through a resistor R36 the capacitor begins to charge C10.
So, ten pulses were received at the counter input. Logical 0 signal at the tenth output of the microcircuit DD6 (pin 11) will go to the element DD8 and is inverted by him. The output signal of the element will turn on the transistor VT22. Relay K25 will operate. Through group, contacts K25.1 it will connect the device TA-10 with the device TA-1.
2…3 s after dialing the number, the capacitor C10 will charge so much that relay K15 will operate. His contacts K 15.1 will send a logical 0 signal to the input of the element DD3.1 (now pulses to the counter input will not pass through it, which means that interference that could cause a typing error will not pass through) and at the same time they will turn off the transistor collector VT1 from the common wire. The generator, assembled on logical elements, will start working DD1.4, DD2.4 and transistor VT1. The generator pulse frequency is approximately 0.2 Hz. With this frequency the relay contacts K11.1 will connect the communication line wire of the TA-10 telephone set (through a resistor R24) then to winding II of the transformer T1, then to the base of the transistor VT5.
If the line is healthy, the AC call current will flow through the resistor R27 and create a voltage drop across it, opening the transistors VTJ, VT8. At the same time, in the line of the device TA-1 AC voltage with a frequency of 400 Hz will be supplied, and the first subscriber will hear long intermittent ringing tones. And in the device TA-10 the bell will ring at this time.
When the tenth subscriber picks up the handset, the relay will operate K13. Contacts K13.1 it will open the emitter circuit of the transistor VT3 and turns off relay K11, and a group of contacts K13.2 opens the resistor terminals R12 and supplies voltage to the LED NOW. Subscribers can carry on a conversation. As soon as they hang up, the telephone exchange will return to its original state.
So that when dialing a relay number K14 did not release, a delay chain was introduced into the station R25 C4 R26. Diode VD25 protects the emitter junction of the transistor VT7 from the effect of reverse voltage on it, and the capacitor C7 smooths out voltage ripples with a frequency of 50 Hz based on the transistor VT8. Diode VD37 promotes rapid discharge of the capacitor C10 when returning the station to its original state.
The telephone exchange is powered by two stabilized sources. The first one is assembled on diodes VD26 - VD29, zener diode VD34, transistor VT9. It provides the supply voltage to the microcircuits. The second, assembled on diodes VD30 - VD33, zener diodes VD35, VD36 and transistor VT10, powers electronic relay circuits. The operation of this source is controlled by an LED H.L.2.
Rice. 6. Location of parts on the subscriber node board
Rice. 7. Location of parts on the signal and control unit board
The following parts are used in the station: Transistors VT1 - VT6, VT8, VT11, VT 12 - any of the KT312, KT315, KT603 series; VT7 - any of the KT203 series (except KT203A), MP25, MP26; VT9, VT10 - KT801 KT807, KT815, KT817 (except KT815A, KT817A) with any letter indices. SCR VS1 - VS10 - any from the KU101 series. LEDs - any of the AL 102, AL 112, AL 307 series. Diodes VD26 - VD33 can be D7, D226, KD209 with any letter indices, the rest can be any of the D9 series (except D9B), D311, D220, D223. Capacitors - K50-6. Electromagnetic relays K1 - KP, K15–K25 - RES-15, passport RS4.591.004, K12 - K14 - RES-47, RF passport4.500.408. Transformer 77 is made on a strip magnetic wire ШЛ16X25. Winding I contains 2200 turns of PEV-20.11 wire, winding II - 360 turns PEV-20.12, winding III - 70 turns PEV-20.33, winding IV - 240 turns PEV-20.23. The power switch and telephone sets are the same as in the previous design. Most of the parts of the automatic telephone exchange are placed on four boards (Fig. 6 - 9), made of textolite 1.5 mm thick. Each board contains a functionally complete unit or block, shown in the block diagram (see Fig. 4). This allows you to make changes and improvements to the design of individual cascades and units, as well as replace units with others developed independently. In addition, you can use printed wiring. For these reasons, only drawings of the location of parts on the boards are given. The connections between the parts on the boards are made with a single-core mounting wire with a diameter of 0.3...0.4 mm in polyvinyl chloride insulation. The pin part of the MPH32 connector is attached to each board. The socket parts of the connector are installed on a common board (Fig. 10). To securely fix the boards in a vertical position, two PCB plates measuring 130×10 mm are used, in each of which four grooves are cut, 0.5 mm wider than the thickness of the mounting board material, and 3...4 mm deep. These plates are mounted on a common board using six metal stands. A power transformer is also mounted on the common board.
Rice. 8. Location of parts on the dial board
Rice. 9. Location of parts on the power supply board
The PBX nodes are housed in a metal case with dimensions of 210X140x100 mm, on the top panel of which there is a strip with clamps for connecting communication lines of telephone sets, a power switch, a fuse holder with a fuse and LED diodes.
If the station is assembled without errors and from serviceable parts, its setup comes down to selecting resistors R13, R17 - R20, determining the frequency of generators. If, after switching on, the station does not work, the search for errors and malfunctions should be carried out in the following sequence.
First, the voltages of the power supplies are measured. On capacitor C7 the voltage should be 4.8...5.2 V, on capacitor C9- 22...25 V. Then check the current consumed from the 5 V source by the dialing unit - it should be 120... 160 mA (but not more than 200 mA). Applying impulses to the input C1 microcircuits DD4, check the operation of the counter and decoder (at the same time, the outputs 2 And 3 microcircuits DD4 a logic 0 signal must be supplied). The operation of the remaining nodes - subscriber, signals and control - is checked in conjunction with all the others.
Electronic dialer
The described telephone exchanges use telephones with a mechanical dialer. It will become more convenient to use the device if you equip it with a push-button (touchpad) electronic dialer. Then to call the subscriber you just need to press the appropriate button.
Rice. 10. Fastening node boards and power supply
A diagram of a device with such a dialer is shown in Fig. 11. It is based on a number-pulse generator made on microcircuits DD1 - DD3. It generates the number of pulses corresponding to the number of the pressed button (switches S.B.1 - SBW). On logical elements DD1.3, DD1.4 a generator has been assembled that generates pulses with a repetition frequency of 15 ... 20 Hz, which are fed to a binary decimal counter DD2. Elements DD1.1 And DD1.2 used in a standby multivibrator, which eliminates the bounce of contacts of push-button switches.
Assume that the telephone receiver is off-hook and the moving contacts of the lever switch S.A.1 took a different position compared to that shown in the diagram. The elements of the pulse number generator are supplied with supply voltage. Transistors VT1, VT2 closed, on terminals 2 And 3 microcircuits DD2 - logical level 1, at all counter outputs - logical level 0. At the outputs 2 - 11 microcircuits DD3 - logic level 1.
When you press the button of any of the switches, for example S.B.10, via diode VD1 and resistor R2 The capacitor will charge quickly NW, transistors VT1, VT2 will open, and at the conclusions 2 to 3 microcircuits DD2 the level will be logical 0. Counter DD2 ready to receive impulses. Simultaneously for withdrawal 2 element DD1.1 Logic level 1 arrives, and the logic gate generator starts working DD1.3, DD1.4. At the same time, at the decoder terminals DD3 the logical 0 signal appears one by one. As soon as it appears on the output 11, through closed contacts of a push-button switch S.B.10 it will go to the input of the element DD1.1, and the generator will turn off. The switch button can now be released. From the generator (pin 11 of the microcircuit DD1) to the base of the transistor VT3 exactly ten pulses will arrive. The same number of times an electronic key on transistors VT3, VT4 closes and opens the line (via telephone B.F.1 and microphone VM1), which will trigger the corresponding relays in the telephone exchange. 2...3 s after releasing the button, the capacitor NW discharged through resistors R3, R4, and microcircuit DD2 will be set to its original state.
Rice. 11. Diagram of a telephone with an electronic dialer
Let's consider the operation of a telephone with a push-button dialer in various modes. In the initial state, the handset lies on the device, and the contacts of the lever switch S.A.1 connect the call to the line HA1 through a capacitor C5 The battery is disconnected. When the handset is picked up, the hook switch contacts turn on the power and connect the transistor switch, telephone and microphone to the line. Transistor VT4 is open because its base is connected through a resistor R9 to the negative terminal of the battery. The line in this case is closed through the low resistance of the transistor VT4, phone and microphone. When a pulse arrives at the transistor VT3 transistor VT4 closes - the line resistance increases sharply.
Let's now get acquainted with the operation of the battery disconnect unit G.B.1 from the elements of the device - it is assembled on transistors VT5 - VT7. When the moving contact of the upper switch group S.A.1 connects to the bottom contact in the circuit, the capacitor begins to charge C4. At this time the transistor VT7 open and power is supplied to the microcircuits. You can press the switch button with the number of the desired subscriber. After some time (tens of seconds), determined mainly by the capacitance of the capacitor C4 and resistor resistance R10, field effect transistor opens VT5, which causes the transistor to turn off VT7. Now the power circuit current will be determined mainly by the resistance of the resistor R11 and resistor resistance R9, ensuring the open state of the transistor VT4 (conversational current flows through the collector-emitter section of this transistor). To call the subscriber again, you need to lower the handset onto the device so that the contacts of the lever switch return to their original position and discharge the capacitor C4, and then pick it up.
The power battery can consist of four D-0.25 batteries connected in series or galvanic cells. Capacitor C5- type MBM, MBGO, KLS for a rated voltage of at least 60 V, other capacitors - K50-6 or others. Pushbutton switches S.B.1 - S.B.10 - any design. It is convenient to use, for example, blocks of buttons from broken computers and microcalculators.
Some of the device parts are placed on a board made of foil fiberglass (Fig. 12). The board has an MPH14-1 connector, the pin numbering of which is shown in Fig. And numbers with strokes. The board and other parts are installed in the body of the telephone, from which the dialer, matching transformer and other unnecessary parts have been removed.
Rice. 12. Printed circuit board (A) electronic dialer and the location of parts on it (b)
Setting up the device begins with installing a jumper between the emitter and collector of the transistor VT7. After this, selecting a resistor R1 set the generator frequency to 15…20 Hz. Then remove the jumper and set up the battery disconnect unit. By disconnecting the resistor R9, instead of a resistor R11 solder a series-connected constant resistor with a resistance of 1 kOhm and a variable resistor with a resistance of 15 kOhm, and connect a milliammeter to the open circuit of the power supply. 20...30 s after turning on the power, when the capacitor C4 will charge to the transistor opening voltage VT5, by moving the variable resistor slider in the direction of increasing resistance, the current is set to 0.7...! mA. Measure the total resulting resistance and solder a constant resistor of the same resistance into the board. Reconnect the resistor R9.
In conclusion, it should be noted that the dial button must be held down for 0.5...! s so that the entire series of pulses is entered into the ATS counter. In addition, the telephone set must be connected to the PBX line in accordance with the polarity indicated on the diagram.
ELECTRICAL CIRCUIT DIAGRAMS OF FOREIGN TE
The diagram shown in Fig. 4.7 is used in handset phones and is practically not found in desktop-type telephones. The only advantage of this scheme is its simplicity. Everything else, unfortunately, is shortcomings. Transistors VT2, VT3 with resistors R9, R10, R11 represent a pulse switch circuit, the operation of which was discussed in section 3.4 (Fig. 3.34). Transistor VT2 in this circuit additionally matches the output signal of the microphone with the input of transistor VT4, which amplifies the microphone signal by current. Transistor VT3 operates in switch mode and does not perform any other functions.
Due to the lack of an amplifier for the received signal from the line, audibility in telephones using such a scheme is quite low. This drawback can be eliminated by using a dynamic head, but in this case the microphone signal will weaken. This type of circuit can only be used with those ENN ICs whose IR output is open drain. It differs from other schemes in the increased line voltage in conversational mode (10 - 15 V).
The supply voltage (about 3 V) of the electret microphone is removed from resistor R14. Capacitor C5 in the circuit of the dynamic head BF1 is a separating capacitor.
In Fig. Figure 4.8 shows a diagram that is most often found in desktop-type telephones and handsets produced in Southeast Asian countries. The circuit is used with various dialer chips (KS5805A, KS5851, UM9151-3, etc.). The functional units of this circuit are discussed in detail in the corresponding chapters.
In Fig. Figure 4.9 shows a diagram of a telephone with additional memory for 10 numbers. The procedure for working with additional memory is described in section 2.8. The operation of IR is described in section 3.4 (Fig. 3.34). The conversational unit is designed according to the type of diagram shown in Fig. 3.36 section 3.5. Quite often, this scheme also uses the conversational node shown in Fig. 3.38.
In Fig. 4.10 shows a diagram of the BELOGRADCHIK telephone made in Bulgaria with additional memory for 10 numbers. The scheme has good characteristics conversation node. Zener diode VD5 is protective. Diode VD9
in conversational mode, it blocks the pulse key, since in this mode the NSI output (pin 9) of the DD1 IC has voltage "high" level.
During dialing, the conversational node is turned off by transistors of the conversational key VT1, VT2. The cathode of the diode VD9 is disconnected from the neutral wire, allowing the operation of a pulse switch made on transistors VT3, VT4.
The IC is powered by diodes VD6 - VD8, VD11.
In Fig. Figure 4.11 shows a diagram of a TA with the "HOLD" mode.
This mode works as follows. In conversational mode, when the handset is off-hook, transistors VT1, VT2 are locked. When you press the "HOLD" button, transistor VT1 opens, which opens transistor VT2. Current flows through open transistor VT2, resistor R8, R12 and diode VD10 and opens transistor VT3. Transistor VT3 bypasses microphone VM1. At the same time, the current through the VD16 LED increases, the brightness of which increases.
Now, if you place the handset on the device, switch SB1 will return to its original state shown in the diagram. In this case, the connection to the line will be maintained through the circuit: open transistor VT2, resistor R8, diode VD11, LED VD16. In this mode, you can switch to a parallel phone and continue the conversation.
When you pick up the handset on a parallel telephone, the latter is connected to the line, and being an additional resistance, it lowers the line voltage. Since the voltage on capacitor C2 has not changed at this moment, the greater potential at the base of transistor VT2 closes it and the first telephone is disconnected from the line.
In Fig. Figure 4.12 shows a diagram of a TA with frequency dialing. In its construction, the circuit is very similar to the circuit shown in Fig. 4.8 and differs from it only in that the operation of the automatic telephone exchange is controlled by a multi-frequency code 2 out of 8, and not by sending DC voltage.
In Fig. Figure 4.13 shows a diagram of a TA made on the basis of the UM9151 microcircuit. The bias voltage at the output of the open-drain pulse switch (pin 9) is supplied from the logical output of the IC talk key (pin 13) through resistor R16. This inclusion of IR eliminates the direct influence of line voltage on the output of the IR IC, which reduces the likelihood of the dialer chip failing.
In Fig. Figure 4.14 shows a diagram of the "GALAX" telephone set, model UP-722TP. The TA body is made of transparent plastic. When an inductor call signal arrives, multi-colored neon lamps LP1 - LP5 perform the function of a call light indication. In conversation mode and during dialing, LEDs LED1 and LED2 illuminate the telephone keypad.
In the TA, the diagram of which is shown in Fig. 4.15, it is possible to operate in both pulse (PULSE) and frequency (TONE) modes. The procedure for programming the NM9112A IC is discussed in section 2.9. The TA conversational node consists of two independent nodes, one of which provides operation with the handset, the other - the "HANDSFREE" mode, i.e. work with a microphone and dynamic head built into the TA body, which makes it possible to talk on the phone without picking up the handset and have your hands free.
In the left position of switch SW1.2, according to the diagram, the handset is connected, in the right position the “HANDSFREE” mode is implemented.
In Fig. 4.16 shows a typical electrical circuit diagram of TA brand Tel 01 and FeTAr from SIEMENS. The main difference of the circuit is that the pulse switch is made on a p-channel high-voltage field-effect transistor BSS92 (the domestic analogue is KP402A, produced by JSC SVETLANA in St. Petersburg). The PSB4500 conversational node IC is functionally no different from the TEA1068 IC, discussed in detail in Chapter 3. The PSB8510-1 IC is a tone-pulse dialer, the operation of which is programmed by pins 9 and 20 (by connecting to the power supply plus, the common pin, or remaining unconnected). Connecting P1 and P2 according to the diagram in Fig. 4.16, the pulse mode of operation of the IC is set by default, the pulse coefficient is 1.5 and a programmable pause when dialing a number is 3 s. SIEMENS telephone microcircuits will be discussed in detail in the next edition.
Operation of the circuit nodes shown in Fig. 4.17 - 4.19, is described in detail in the relevant sections.
