KR900000840B1 - Circuit for monitoring of exchange trunk - Google Patents

Abstract

The automatic recognition circuit comprises an over current protecting circuit (10) which is connected in parallel to private exchanger lines (L1,L2) protecting elements of the using circuit by lowering the voltage under the proper voltage, the first rectifying circuit (20), a transformer (100), a second rectifying circuit (90) which interrupts the direct voltage and detects a ring signal, a ring signal recognising circuit (80) which outputs a ring signal to a proper logic level, a line recognizing circuit (70) determining whether lines (L1,L2) are connected to the telephone exchanger or not, a dial pulse generating and relay control circuit (40), and a transmitting/receiving seperation or gain control circuit (50).

Description

Trunk Line Type and Trunk Line Automatic Detection Circuit

1 is a block diagram of a trunk line type and trunk line automatic detection circuit according to the present invention.

2 is a specific circuit diagram showing the embodiment of FIG.

3a-c is a waveform diagram for the operation of the trunk line relay when receiving.

4a-c is a waveform diagram for the operation of the trunk line relay when the telephone exchange is a mechanical type.

5a-c is a waveform diagram for the operation of the trunk line relay when the telephone exchange is electronic.

* Explanation of symbols for main parts of the drawings

10: overvoltage protection circuit 20: first rectifier circuit

30: trunk line relay circuit 50: transmission / reception separation and gain control circuit

40: Dial pulse generation and trunk line relay control circuit

60: frequency detector 70: line detection circuit

80: ring signal detection circuit 90: second rectifier circuit

The present invention relates to a circuit capable of automatically detecting the type of CO line and CO line using a private exchange. In particular, the present invention detects whether an CO line is electronic or mechanical and determines the available line of the CO line, thereby making a call between the subscriber and the CO line. It relates to a circuit that can be controlled.

In the normal private exchange, when the subscribers were able to make a trunk line call, if the trunk line telephone system was selected, the number of lines available for the trunk line had to be selected.

In the conventional private exchange, the telephone line system and the possibility of using the trunk line can be used in a memory device installed in the exchange, in particular, in a ROM (Random Only Memory). The number of the haute was stored in advance before the extension subscribers call, and when the extension subscribers wanted to talk to the CO line, the regular data value of the memory device under the control of the central processing unit (CPU) could be retrieved to make the call. Therefore, when the telephone system of the CO line or the number of lines of the CO line is changed, the contents stored in the storage element have to be changed.

Also, in the trunk line circuit of a conventional private exchange, when the telephone line system is mechanical, the mechanical relay is turned on and off to send dial pulses corresponding to the numbers pressed by the subscribers to the trunk line to make-break. Signal has been generated. However, when a mechanical pulse is generated using such a mechanical relay, an electromagnetic disturbance signal is generated by the magnetic field generated when the magnet is driven, and a harmonic disturbance signal is generated due to the generation of harmonics. It has had a bad effect, such as degrading call quality.

Therefore, an object of the present invention is to provide a circuit that can automatically detect the type of telephone line and the use of the trunk line.

Still another object of the present invention is to provide a circuit capable of preventing electromagnetic interference signals and high frequency interference signals by transmitting dial pulses using an electronic relay.

Another object of the present invention is to provide a circuit capable of gain adjustment of a transmission signal and a reception signal independently by providing transmission and reception separation and gain control circuits in a communication path.

In order to achieve the above object of the present invention, an overvoltage protection circuit for preventing the occurrence of a voltage above a predetermined voltage so that the abnormal voltage does not affect the internal circuit of the private exchange when the abnormal voltage coming through the trunk lines L1 and L2 occurs, First and second rectifier circuits for maintaining the output polarity constantly, even if the trunk line of the telephone station is arbitrarily connected to L1 and L2, ring signal sensing circuit for detecting the incoming call, and whether the trunk line is usable. Line detection circuit 70 for detecting whether L1 or L2 is connected to the trunk line, and when the telephone line is received, the line detecting circuit 70 turns on and generates a dial pulse according to the dialing of the subscriber when the trunk line is mechanical. Dial pulse generation and CO line relay control circuits that generate on / off control and dial pulses of the trunk line relay that acts on and off. Transmitting and receiving and gain control circuits that can independently adjust the gain of the received signal at the time of transmission, transmission, or reception, and ring signal detection for detecting a ring signal when a ring signal is input from the trunk line side. A circuit, a line detecting circuit for detecting whether trunk lines L1 and L2 trunk lines are connected, and a frequency checker for determining whether the trunk line is a mechanical telephone system or an electronic system according to the presence or absence of a dial tone transmitted by the trunk line. .

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a block diagram of a circuit capable of automatically detecting the type of telephone line of a trunk line and whether a trunk line is used, according to the present invention, in which L1 and L2 represent trunk lines connected to a telephone station; The overvoltage protection circuit 10 prevents the occurrence of an abnormal voltage above a predetermined voltage so that the occurrence of an abnormal voltage coming into L2 does not affect the internal circuit of the private exchange, and the trunk line of the telephone station is arbitrarily selected to the trunk lines L1 and L2. The first rectifying circuit 20 and the second rectifying circuit 90 to keep the output polarity constant even when connected, the ring signal detecting circuit 80 for detecting whether the telephone is connected, and the trunk line can be used. The line detecting circuit 70 for detecting whether L1 and L2 are connected to the trunk line, and when the telephone is received, the line detecting circuit 70 is turned on and when the telephone line is mechanical, The trunk line relay 30 which acts on and off to generate ear pulses, the dial pulse generation and trunk line relay control circuit 40 which generates the on / off control and the dial pulse of the relay, the transformer 100, and the transmission. Alternatively, the transmission / reception separation and gain control circuit 50 which can independently adjust the gain of the transmission signal or the reception signal at the time of reception, and whether or not the CO line is a mechanical switching method or an electronic telephone method according to the presence or absence of a dial tone transmitted from the CO line side. It is composed of a frequency checker 60 to determine.

When the CO line is not connected to the CO lines L1 and L2 at this time, since the call power of the CO line cannot be input, the DC voltage is not applied to both ends of the CO lines L1 and L2. The output of the line sensing circuit 70 and the ring signal detecting circuit 80 is also absent from the output of the two rectifying circuits 90, which also indicates the logic level of the low state (hereinafter referred to as the "0" state). Therefore, when the trunk lines L1 and L2 are not connected to the trunk line exchanger, the logic level of 0 is maintained at the output lines 130 and 140 of the line sensing circuit 70 and the ring signal sensing signal 80, respectively. The central processing unit (CPU) (not shown) shows that the trunk lines L1 and L2 are not connected to the telephone station by the logic level state of the output line 130.

On the other hand, when the trunk lines L1 and L2 are connected to the communication line of the telephone station, DC voltages of 0 volts and -48 volts (or -48 volts and 0 volts) are applied to the trunk lines L1 and L2, respectively.

Therefore, this DC voltage causes polarity shaping in the first rectifier circuit 20 made of a conventional bridge type diode. The first rectifier circuit 20 can be used regardless of the input voltage even if the CO line sends 0 volts to the trunk line L1, -48 volts to the trunk line L2, or -48 volts to the trunk line L1, and 0 volts to the trunk line L2. In this case, the voltage at the output point A becomes positive and the voltage at the output point B becomes negative so that the voltage difference between A and A 'is +48 volts.

Therefore, this DC voltage is input to the line sensing circuit 70 and outputs a logic level in a high state (hereinafter referred to as a 1 state state) by means of sensing the shaped DC voltage.

The output of the line detection circuit 70 is applied to the CPU, and when detected as a “high logic” state, the CPU may recognize that the corresponding trunk lines L1 and L2 are available for trunk lines. On the other hand, the second rectifier circuit 90 having the DC blocking means connected to the input side of the conventional bridge diode rectifier circuit rectifies the ring signal, which is the AC signal, only at the input of the ring signal to positively output the output terminals B and B '. The DC voltage of the output is output. When the ring signal is not input, the DC terminal means does not output the DC voltage to the output terminals B and B '. Therefore, in the output line 140 of this circuit, the logic in the state of " 1 " by the ring signal detecting circuit 80, which is a means for detecting the DC voltage output to the output terminals B and B 'rectified at the time of the above-mentioned ring signal input, is output. Make the level appear.

The output of the ring detection circuit 80 is applied to the central processing unit (CPU), whereby the central processing unit (CPU) can detect the presence or absence of a call according to the logic state of this signal.

Therefore, when the trunk lines L1 and L2 are connected to the telephone line communication path, the output of the line detection circuit 70 is changed from the 0 state to the 1 state, and when the ring signal is input from the trunk line, the ring signal detection circuit 80 As the output changes from the 0 state to the 1 state, the CPU knows that the CPU is connected to the trunk line, and also detects the ring signal to be input. Therefore, when the ring signal is input to the trunk line terminals L1 and L2 during reception, the output of the ring signal detection circuit 90 is in the state of ＂1＂, and the central processing unit (CPU) that detects this logic state generates the dial pulse and controls the trunk line relay. The circuit 40 generates a trigger signal. Then, the dial pulse generation and the CO line relay control circuit 40 turn on the CO line relay circuit 30, and thus the signal input to the CO line L1, L2 is induced on the secondary side of the transformer 100, and the signal is transmitted and received and separated. Through the receiving circuit of the gain control circuit 50 is input to the call path 110 is input to the extension subscriber's telephone.

On the other hand, the function of the frequency checker 60 is, when the system of the private exchange according to the present invention, according to the control of the central processing unit (CPU) as described above by the dial pulse generation and the trunk line relay circuit through the trunk line relay control circuit 40 The relay of (30) is turned on, and an arbitrary telephone number is sent to the trunk lines L1 and L2 with a complex frequency to analyze whether the trunk line is an electronic switch or a mechanical switch. That is, when the subscriber subscriber switch of the telephone line 110 is turned off when the system is turned on, the telephone line of the CO line and the subscriber is opened, thereby inputting a dial tone (350MZ + 440MZ) supplied from the CO line. 60 decodes a dial tone and outputs a signal of the '0' state to the output line 120. Thereafter, if the above-mentioned DTMF signal is transmitted to the trunk line and a predetermined time has elapsed and no dial tone is input from the switchboard side trunk lines L1 and L2, the frequency detector 60 does not detect the dial tone. As a result, the COS is an electronic telephone exchange. That is, when the CO line is an electronic exchange, the DTMF signal through the CO lines L1 and L2 is recognized, so that the CO line stops supplying the dial tone.

In addition, if the dial tone continues to be input after the predetermined time hardening (the output of the frequency checker 60 is in the 0 'state), the trunk line exchanger is proved to be a mechanical telephone exchange system. This is because the CO line is a mechanical exchange, so the DTMF signal is not recognized through the CO lines L1 and L2, and thus the state of supplying the dial tone is maintained. Therefore, according to the output state of the frequency detector 60, the CPU determines that the trunk line exchanger is an electronic or mechanical exchange system, and does not show the exchange method of the trunk line exchangers connected to the trunk lines L1 and L2. The memory area is stored under the control of the central processing unit.

Now, when the extension subscriber's phone is electronic and the extension subscriber wants to transmit to the trunk line through the call path 110, the telephone exchange method of the trunk line exchanger connected to the trunk lines L1 and L2 is electronically determined according to the above-described determination of the telephone exchange method. In the exchange method, as described above, the relay of the trunk line relay circuit 30 is turned on according to the control of the central processing unit, so that the signal of the subscriber is transmitted through the communication path 110 and the transmission / reception separation and gain control circuit 50 is performed. The transmission is transmitted to the trunk line exchange through the transmission separation and gain control circuit and the transformer 100, the trunk line release circuit 30, and the first rectifier circuit 20.

On the other hand, if the telephone exchange method of the trunk line switch is electronic and the subscriber's telephone is mechanical, the dial pulse of the subscriber can be converted into a complex frequency using a known DTMF conversion circuit and inputted into the call path 110. However, if the telephone exchange system of the trunk line switch is mechanical, the dial pulse corresponding to the dial digit selected by the station subscriber should be sent to the trunk lines L1 and L2, which relays the relay of the trunk line relay circuit 30 under the control of the central processing unit. It can be achieved by intermittent to the generation of the dial pulse and the output of the trunk line relay control circuit 40.

Therefore, after the extension subscriber finishes dialing, the trunk line relay is turned on and a call is made when a person who wants to call through the trunk line exchange is called.

FIG. 2 is a circuit diagram of one embodiment embodying the block diagram of FIG. 1 according to the present invention, wherein R1-R21 is a resistor, C1-C13 is a capacitor, VR1 is a variable resistor, D1 is a diode, and D2 is a zener diode. VCC is the supply voltage.

The diaak D1 corresponding to the overvoltage protection circuit 10 of FIG. 1 prevents destruction of other devices by outputting a voltage below a predetermined value when an abnormal voltage of a high voltage is input through the trunk lines L1 and L2. Also, the first rectifying circuit 20 of FIG. 1 is a rectifying circuit diagram of a conventional bridge diode, and 91 of the second rectifying circuits 90 is also a rectifying circuit of a conventional bridge diode described above, both of which are trunk lines. It plays the role of outputting with the polarized polarity regardless of the polarity of DC voltage (0V and -48V) input from the trunk line exchanger connected to L1 and L2. That is, regardless of whether 0 volts is input to the trunk line L1, -48 volts to the trunk line L2, or -48 volts to the trunk line L1, or 0 volts is input to the trunk line L2, the first rectifier circuit 20 is positively connected to the output terminal A. It can be seen that the voltage of is output to the output terminal, A ', a negative voltage so that a 48V voltage is always generated.

However, the second rectifying circuit 90 is connected to the trunk line rectifier 91 with the trunk line L1 or L2 through the resistor R16 and the capacitor C9 as shown in the drawing, so that when a ring signal is not input from the trunk lines L1 and L2, The DC voltage is cut off by the DC blocking capacitor C9 so that the rectified DC voltage does not appear on the output terminals B and B 'of the second rectifying circuit 90. On the other hand, when the ring signal is input, the ring signal, which is an AC component mixed with the DC voltage, is rectified and output to the output terminals B and B '. As described above, it can be seen that a positive voltage is generated at the output terminal B and a negative voltage is generated at the output terminal B '.

When the ring signal detection circuit 80 outputs the ring signal rectified from the output terminals B and B 'of the second rectifying circuit 90 as described above, the signal is output to the light emitting diode 83 constituting the photocoupler 81. ) And the zener diode D2, which causes the phototransistor 82 to conduct as the light emitting diode 83 is turned on, and outputs a voltage of the power supply voltage VCC to the output line 140. Capacitor C8 is used to reduce ripple due to the rectified ring signal, and output line 140 outputs the voltage of the VCC, that is, the high voltage state, when the ring signal is input.

In addition, the line detecting circuit 70 inputs a DC voltage (+48 volts) output from the output terminals A and A 'of the first rectifying circuit 20 when the trunk line L1 and the local exchange are connected to the photocoupler 71. The phototransistor 72 is turned on when the light emitting diode 73 constituting the light is turned on, and the output line 130 outputs the voltage of the VCC, that is, the logic level of the “high” state.

에 연결한다. 따라서 라인(42)으로 입력하는 펄스가 다운에지 상태일시 시간 T=1.1 VR1.C1만큼 라인(43)으로 출력하는 펄스가 ＂하이＂상태를 유지하다가 ＂로우＂상태를 유지한다. 그러므로 다이얼펄스 발생 및 국선릴레이 제어회로(40)는 송수신시 라이(42)으로 입력하는 펄스가 ＂로우＂에서 ＂하이＂로 되고 출력라인(43)은 ＂하이＂상태에서 ＂로우＂상태로 변한다. 또한 송신시 전화국 교환기가 기계식이라 하면 전술한 바와 같이 내선가입자가 다이얼링한 디지트에 대응하는 다이얼펄스의 발생을 위해, 중앙처리장치는 해당 디지트에 해당하는 100ms단위의 펄스신호를 라인(42)으로 출력하고, 이 펄스에 의해 단안정멀티바이브레이터(41)는 상술한 식 T=1.1 VR1.C1에 의한 약 66mSec 및 33mSec의 메이크와 브레이크 신호를 발생하여 라인(43)으로 출력한다.The dial pulse generation and trunk line relay control circuit 40 is a monostable multivibrator. The input line 42 is connected to the central processing unit, and the output line 43 is inverted.

Connect to Therefore, the pulse outputted to the line 43 by the time T = 1.1 VR1.C1 when the pulse inputted to the line 42 is in the down-edge state maintains the high state and then the low state. Therefore, when the pulse pulse is generated and the CO line relay control circuit 40 transmits / receives, the pulse inputted to the lie 42 goes from low to high and the output line 43 changes from high to low. . Also, if the telephone exchange is mechanical when transmitting, in order to generate dial pulses corresponding to the digits dialed by the subscriber, as described above, the central processing unit outputs a pulse signal of 100 ms units corresponding to the digits to the line 42. By this pulse, the monostable multivibrator 41 generates make and brake signals of about 66 mSec and 33 mSec according to the above-described formula T = 1.1 VR1.C1 and outputs them to the line 43.

Meanwhile, the CO line relay circuit 30 includes a semiconductor relay 33, a resistor R17, and a power supply voltage VCC. The CO line relay circuit 30 includes a light emitting diode (D) by the above-described dial pulse generation and the output of the output line 43 of the CO line relay control circuit 40. The current path of 31 is controlled to control the on / off of the relay 32. Therefore, when the output line 43 is in the low state, the light emitting diode 31 is turned on and the relay 32 is in the on state, and when the output line 43 is in the high state, the relay 32 is turned off. It becomes a state.

The transformer 100 is connected to the primary side with a winding ratio of 1: 1 as shown by the capacitor C10 for AC bypass and the resistor R18 serving as a direct current load. Transmitting and receiving separation and gain control circuit 50 is connected to the secondary side of the voltage transformer 100, and this circuit is composed of a transmission separation and gain control circuit 300 and a reception separation and gain control circuit 200. The received signal induced on the secondary side of the transformer 100 is amplified through the reception separation and gain control circuit 200 and input to the extension subscriber line 110 and the frequency detector 60. In addition, the transmission signal of the subscriber station is input through the subscriber subscriber line 110 through the frequency detector 60 and the transmission separation and gain control circuit 300 and the transformer 100 to the switching center of the telephone station.

In this case, when the transmission signal of the extension subscriber is output to the trunk line through the operational amplifiers 310 and 320 constituting the communication path 110 transmission separation and gain control circuit 300, the signal is again received and separated. Through the operational amplifiers 220 and 210 constituting the gain control circuit 200, the phenomenon in which the transmission signal is fed back to the communication path 110 through the path of the resistor R6 and the capacitor C3 must be prevented. The feedback is also returned to the telephone exchange center through the reception separation and gain control circuit 200 and the transmission separation and gain control circuit 300 and the transformer 100).

Therefore, in order to prevent the phenomenon, the resistance R1 is equal to the combined impedance of the resistor R1 and the secondary side of the transformer 100 at the node point 230 and the combined impedance of the resistors R2 and R3 at the node point 230 are the same. By designing by setting the value of R3, if the input signal of the inverting input terminal (-) and the non-inverting input terminal (+) of the operational amplifier 220 is the same, there is no output signal of the operational amplifier 220, so Therefore, the transmission signal is not fed back through the reception separation and gain control circuit 200 during transmission. Similarly, in order to prevent the received signal from being fed back to the telephone exchange, the resistors R6, R7, and R6, R7, and R2 may have the same input signal at the inverting input terminal (-) and the non-inverting input terminal (+) of the operational amplifier 310 as described above. By adjusting the value of R8, it is possible to prevent the reception signal from being fed back to the telephone exchange through the reception separation and gain control circuit 200, the transmission separation and gain control circuit 300, and the transformer 100.

배 만큼 증폭되어 노드점(350)에 나타나고, 이 신호는 다시 가변저항 R10의 조정에 따라

배로 이득이 조절되어 송신분리 및 이득 제어회로(300)에서 출력하고, 이 신호는 전술한 바와 같이 연산증폭기(220)에서 증폭되어 출력되지 않기 때문에 저항R1, 변압기(100)를 통해 전화국 교환기 측으로 송출된다. 전술한 연산증폭기(310)에서의

배의 증폭은 수신분리 및 이득 제어회로(200)를 구성하는 연산증폭기(210)의 출력 임피던스가 0에 가까우므로 노드점(330)은 접지상태로 되며, 따라서 저항 R7과 R8및 연산증폭기(310)으로 구성되는 회로는 비반전 증폭기로 작용하기 때문이다.Therefore, the transmission signal of the civil war subscriber entered through the communication path 110 appears at the node point 340, and this signal is transmitted from the operational amplifier 310 constituting the transmission separation and gain control circuit.

It is amplified by twice and appears at the node point 350, and this signal is again in accordance with the adjustment of the variable resistor R10.

The double gain is adjusted and output from the transmission separation and gain control circuit 300. Since the signal is not amplified and output from the operational amplifier 220 as described above, the signal is sent to the telephone exchange center through the resistor R1 and the transformer 100. do. In the above-described operational amplifier 310

Since the amplification of the double is the output impedance of the operational amplifier 210 constituting the reception separation and gain control circuit 200 is close to 0, the node point 330 is grounded, and thus the resistors R7 and R8 and the operational amplifier 310 This is because a circuit composed of) acts as a non-inverting amplifier.

Similarly, the received signal input from the telephone exchange is transferred to the non-inverting amplifier consisting of the resistors R2, R3 and operational amplifier 220 and the resistors R4, R5 and operational amplifier constituting the reception separation and gain control circuit 200 through the transformer 100. Passed through the inverting amplifier consisting of 210 and passes through the resistor R6 and the capacitor C3 to the subscriber's channel 110.

On the other hand, the frequency detector 60 is composed of two tone decoders 61 and 62 and an end gate 63. The operation of the frequency checker 60 is to turn off the hook switch of the extension subscriber when the system of the private switching system according to the present invention turns off the ring tone supplied from the switchboard of the telephone station to the trunk lines L1 and L2, and then through the call path 110. Dial digits are sent as DTMF signals. Then, if the type of telephone exchange is electronic, the DTMF signal is recognized and the supply of the dial tone is stopped. If the telephone exchange is mechanical, the DTMF signal cannot be recognized.

That is, when a ring tone of two mixed frequencies transmitted to 350HZ + 440HZ is generated, it is input to the input terminals IN of the tone decoders 61 and 62 of the frequency detector 60, and at this time, the tone decoder The order 61 detects an input frequency of 350HZ and outputs a blow state to the output terminal OUT, and the tone decoder 62 detects an input frequency of 440HZ and outputs a blow signal as described above. do. In this case, the tone decoders 61 and 62 have a detection center frequency set by resistors R11, capacitor C5, resistors R20, and capacitor C13, resistors R12 and R21 are load resistors, and capacitors C7 and C12 determine bandwidth. Play a role. Therefore, the frequency detector 60 enters all of the outputs of the tone decoders 61 and 62 when the dial tone is input, and therefore the output of the oragate 63 also becomes the state of 0. However, as described above, after the digit transmission of any DTMF signal, the dial tone is cut off, and the outputs of the tone decoders 61 and 62 become ＂1＂ state, and the output line 120 of the oragate 63 is also ＂. It becomes 1 ＂state. Therefore, it can be seen that the type of telephone station exchange is electronic, and if the type of telephone station exchange is a conventional type, the tone is continuously received, so that the output of the oA gate 63 continues as described above.

3 is a diagram showing the operation of the CO line relay when detecting a ring signal. FIG. 4 is a waveform diagram showing a process of generating a dial pulse by controlling the CO line relay when the switchboard of the CO line is mechanical. FIG. Is a waveform diagram showing a process of outputting a DTMF signal by controlling a CO line relay when the exchange is electronic.

Based on the above configuration, the present invention will be described in detail with reference to FIGS. 3, 4, and 5. In general, the formation of a call path in a private exchange consists of a subscriber circuit, a switching circuit, and a trunk line circuit under the control of the central processing unit. At this time, if the subscriber's telephone is mechanical, the subscriber circuit generates a dial pulse corresponding to the corresponding digit and supplies it to the central processing unit.In the case of the electronic, the DTMF receiver transmits a DTMF signal corresponding to the corresponding digit to 2 bits of 4 bits. It is converted into the difference data and supplied to the CPU. If the switch of the trunk line is electronic, the central processing unit outputs a signal corresponding to the digit to the DTMF transmitter, and the DTMF transmitter converts the data into a DTMF signal and applies it to the trunk line circuit. However, if the switchboard on the trunk line side is mechanical, the central processing unit controls the relay on the trunk line side to generate a dial pulse corresponding to the digit. First, when the telephone line exchanger is not connected to the trunk lines L1 and L2 in the circuit diagram of FIG. 2, since there is no DC voltage (0V-48V) applied to the trunk lines L1.L2, the output terminal A of the first rectifier circuit 20, A 'also has no DC voltage output. Therefore, since the output line 130 of the line sensing circuit 70 is output in the state of '0' and applied to the central processing unit, the central processing unit can know that the trunk lines L1 and L2 are not connected to the telephone station.

On the other hand, when the telephone line exchanger is connected to the trunk lines L1 and L2, a voltage of -48 volts is applied to the trunk lines L1 and L2, and the first rectifier circuit 20 always polarizes the DC voltage to the output terminal A.A '. Since a voltage of +48 volts is output, as described above, the output line 130 of the line sensing circuit & 0 is in the state of # 1.

Therefore, the central processing unit detects that the trunk lines L1 and L2 are connected to the telephone station switch. Here, after the circuit of the present invention is connected to all trunk lines of the private exchange, the central processing unit analyzes the output of the high level state through the line detection circuit of each trunk line, and this number becomes the number of usable lines of the trunk line. . Secondly, after connecting the private exchanger to the telephone exchange, as described above, the method of sensing the manner of the telephone exchange is exchanged, and the transmission of the telephone exchange is analyzed by supply status to determine whether it is electronic or mechanical. That is, when the dial tone (350HZ + 440HZ) is supplied from the telephone exchange, the tone decoders 61 and 62 detect this, respectively, and output a low signal. As a result, the OA gate 63 also outputs the low signal. Thus, the central processing unit can be seen that the dial tone is supplied from the telephone exchange. At this time, if the central processing unit controls to output the DTMF signal for any digit through the communication line line 110, it is supplied to the telephone exchange through the trunk lines L1, L2.

연결된 출력라인(43)은 상기 제3b도와 같은 입력펄스가 업에지에서 제3c도와 같이 ＂0＂상태로 신호를 출력한다. 이때 상기 중앙처리장치에서는 제3b와 같이 계속하여 ＂1＂상태의 신호를 출력하므로, 단안정 멀티바이브레이터(41)는 출력라인(43)으로 계속하여 ＂D＂상태의 신호를 출력한다. 따라서 발광다이오드(31)의 전류통로가 형성되므로, 릴레이(32)가 ＂온＂되어 국선 링신호를 통화로측으로 공급하게 된다.At this time, if the telephone exchange exchange recognizes the DTMF signal as a dialing signal, it stops supplying the dial tone that was being supplied to receive the digit signal, and thus, the toe decoder 61 and 62 cannot detect the frequency of the dial tone. Therefore, the oA gate 63 outputs a “high” signal. The central processing unit therefore detects that the telephone exchange is electronic and records in the memory area that the telephone exchange is electronic. However, if the telephone exchange does not recognize the DTMF signal as a dial signal, it continues to supply a dial tone, which causes the tone decoders 61 and 62 to detect the dial tone so that the oragate 63 is in a low state. Keep it up. Therefore, if the central processing unit continues to supply the dial tone until a predetermined time after the DTMF signal is transmitted, the central office switch determines that the telephone exchange is mechanical and records it mechanically in the memory area. Here, when the ring signal is generated from the trunk line side to the private exchange side, the ring signals are mixed and input based on the DC voltage of -48 volts at both ends of the trunk line L1 and L2. At this time, the DC signal is removed by the capacitor C9 and the rectified ring signal is output to the output terminals B and B 'of the second rectifying circuit 90 by the input ring signal including the AC component. The photocoupler 81 is driven by this rectified signal, the repulsive component is removed by the capacitor C8, and the output line 140 outputs a logic signal of one state as shown in FIG. At this time, the CPU receives a ring detection signal as shown in FIG. 3A and inputs a pulse as shown in FIG. 3B to the input line 42 of the monostable multivibrator 41. Therefore, the inverting terminal of the monostable multivibrator 411

The connected output line 43 outputs a signal in which the input pulse as shown in FIG. 3b is in the '0' state as shown in FIG. 3c at the up edge. At this time, since the central processing unit continuously outputs the signal of the state # 1 'as in the third b, the monostable multivibrator 41 continuously outputs the signal of the state “D” to the output line 43. Therefore, since the current path of the light emitting diode 31 is formed, the relay 32 is turned on to supply the trunk line ring signal to the communication path side.

Therefore, the received signal is transmitted to the subscribers through the relay, transformer 100, receiving separation and gain control circuit 200 to the subscriber's communication path 110.

On the other hand, when the telephone station switch type is mechanical and in a transmission state, the extension subscriber connected to the call path 110 first lifts the hand cell of the telephone, and the hook switch of the telephone is in a hook-off state. At this time, the central processing unit recognizes the hook-off of the subscriber station, and outputs a ＂1＂ state signal to the input line 42 of the monostable multivibrator 41 as shown in FIG. 4a, and thus the output line 43 of the circuit. Is changed to the 0 state, and the relay 32 of the trunk line relay circuit 30 is turned on. Thereafter, when the extension subscriber hears the dial tone supplied from the telephone station and presses the dial number of the person to be called, the central processing unit outputs a pulse signal of 100 ms in one cycle as shown in FIG. 4A to generate a dial pulse for the corresponding digit. At this time, the monostable multivibrator 41 generates the pulse signal as shown in FIG. 4a as the pulse of about 66msec and 33msec as shown in FIG. 4b. This is because dial pulse generation is defined as 33ms make and 66ms brake, with one pulse period of 100ms, so that the pulse period of the monostable multivibrator 41 is adjusted to 66ms (that is, T = 1.1, VR ₁ , C ₁ =). 66 ms). The dial pulse is determined according to the digit value, the pulse period is 100 msec, and the pause time between the digit and the digit becomes 600 ms or more. The output of the monostable multivibrator 41 as shown in FIG. 4B interrupts the trunk line relay 32 of the trunk line relay circuit 30 to generate one pulse every 100 msec as shown in FIG. 4C. For example, when the subscriber presses 3 as the first digit, three pulses are generated by the on and off operation of the relay 32 as shown in FIG. Through the control circuit 200 and the communication path 110 is also transmitted to the subscribers can hear the dial pulse transmission sound. In addition, after all the dial digits are pressed, the relay 32 remains on, and if there is a response from the caller, the telephone call is transmitted through the call path 110, the transmission / reception separation and gain control circuit 50, and the transformer 100. Is done.

On the other hand, when the telephone exchange is of electronic type and is in the transmission state, the input pulse 42 of the dial pulse generation and trunk line relay control circuit 40 goes to the '1' state when the subscriber is hooked off and the output line 43 is the '0' state. Is maintained as in Figs. 5a and b. Therefore, the trunk line relay 32 is turned on as shown in FIG. 5C.

Therefore, the composite frequency signal (the dial signal transmitted from the call path 110) (even though the telephone type of the extension subscriber is mechanical) can be converted to the complex frequency signal using the DTMF chip and mixed with the DC voltage to the 5c. As shown, the waveform is sent to the telephone exchange.

As described above, the CO line type and CO line automatic detection circuit according to the present invention has a function of automatically checking the type of CO line and the CO line number, and can remove various disturbance signals using an electronic relay in synchronization. In addition, since the transmitting circuit and the receiving signal can be separated, the gain of the transmitting signal or the receiving signal can be adjusted independently, and the use of one electronic relay has the advantage that the dial signal can be transmitted.

Claims (3)

The overvoltage protection circuit 10 connected in parallel with the private line trunk lines L1 and L2 for protecting the elements of the circuit used by lowering the voltage below a predetermined voltage with respect to the input of the abnormal voltage and the output of the circuit line are input. In the private exchanger circuit including the first rectifier circuit 20 and the transformer 100 for rectifying the DC voltage at a constant polarity regardless of the polarity of the input DC voltage of the voltage, the voltages at both ends of the trunk lines L1 and L2 are reduced. A second rectifying circuit 90 for inputting and blocking a DC component and detecting and outputting a ring signal; a ring signal sensing circuit 80 for detecting and outputting the detected ring signal at a predetermined logic level; and the first rectification. It detects the output DC voltage of the circuit 20, determines whether the telephone station switch is connected to the trunk lines L1 and L2, and accordingly inputs and receives a line sensing circuit 70 for outputting a predetermined logic level and a predetermined control pulse. CO Line at start Dial pulse generation and CO line relay control circuit 40 which maintains the ON state of the ray 32 and controls dial pulse generation when the telephone station switch is mechanical, and the transformer 100 which drives the relay with the control signal of this circuit. Transmission / reception separation and gain control connected to the trunk line relay circuit 30 connected to the primary side and the secondary side of the transformer 100 to separate the transmission signal and the reception signal to transmit and receive and simultaneously adjust gain. And a frequency checker (60) for determining the exchange method of the exchange with or without a dial tone for any digit number transmitted from the private exchange according to the type of telephone station exchange at the time of system ON. Trunk line type and trunk line automatic detection circuit. 2. The transmission and reception and gain control circuit of claim 1, wherein the transmission and reception separation and gain control circuit 50 includes a transmission separation and gain control circuit 300 and a reception separation and gain control circuit 200 each having amplifiers configured as operational amplifiers. Or a non-inverting amplifier circuit and an inverting amplifier circuit so that feedback does not occur upon reception. 2. A circuit according to claim 1, characterized in that the frequency checker (60) is provided with tone decoders (61, 62) and gates (63) for detecting a dial tone to determine the type of exchange of the telephone exchange.

Images