KR930003483B1 - Trunk circuit for fax - Google Patents

Abstract

The system makes possible that the trunk circuit of private switch board holds jointly a D.C. by-pass circuit, a transformer impedence matching and gain control circuit by using the analog switch. It also provides the circuits that controls the voice communications and facsimile's transmissions and receptions. It comprises a PCM code (14), a CPU (15) for the system control, a the switching control circuit (16) for the first and second switching signal, a fax modem (17), a reception gain setting circuit (18), a transmission gain setting circuit (19), and analog switchs (20,21,22) switched by the 1st and 2nd switching signal.

Description

Facsimile Private Switching Trunk and Shared Circuit

1 is a circuit diagram according to the present invention.

2 is a detailed circuit diagram of one embodiment of the transmission and reception gain setting circuits 18 and 19 during the first phase.

* Explanation of symbols for main parts of the drawings

11 DC bypass circuit 12 transformer

13 impedance matching and gain control circuit 14 PCM codec

15: CPU 16: switching control circuit

17: fax modem 18: reception gain setting circuit

19: Transmission gain setting circuit 20-22: Analog switch

OP1-OP7: OP amplifier R1-R13: resistor

C1-C2: Capacitor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facsimile private exchange trunk circuit and a shared circuit. Particularly, in a facsimile joined to a private exchange, a direct current bypass circuit, a transformer, Impedance matching and gain control circuitry relates to a circuit shared by the facsimile using an analog switch.

Currently, the facsimile has a separate telephone circuit. When making or receiving a call, the facsimile is first connected to the telephone circuit to receive a voice signal, and the facsimile transceiver uses a relay to switch to a modem. After completing the voice call and switching to the facsimile, the voice call becomes impossible again. In addition, DC bypass circuit, transformer, impedance matching and gain control circuit are used separately for DC bypass and hold.

As described above, the conventional facsimile uses a DC bypass circuit, a transformer, an impedance matching and a gain control circuit separately, so that the circuit becomes complicated, the area occupied by the component, and the control is inconvenient. There was also a problem that phone calls were not possible after the conversion to facsimile.

Accordingly, an object of the present invention is to provide a circuit that can share a DC bypass circuit, a transformer, an impedance matching and a gain control circuit of a trunk circuit of a private exchange using an analog switch in a facsimile subscribed to the private exchange. .

It is still another object of the present invention to provide a circuit capable of controlling voice calls and facsimile transmission and reception using an analog switch in a facsimile.

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

1 is a circuit diagram according to the present invention, which matches a DC bypass circuit 11 connected to lines T and R to bypass DC and a public telephone network connected to the DC bypass circuit 11. A transformer 12, an impedance matching and gain control circuit 13 connected to the transformer 12 to match input / output impedance and controlling gain, and a received analog voice signal to digital PCM (Pluse Code Modulation) voice data. A PCM codec (14) for converting and outputting input digital PCM voice data into an analog voice signal and transmitting the same; a central processing unit (CPU) 15 for controlling the system; A switching control circuit 16 for outputting first and second switching signals under control, a FAX modem 17 for modulating a fax transmission / reception signal, and the fax modem 17 The gain of the received signal of the fax is A reception gain setting circuit 18 for setting and outputting according to (17) and a fax modem 17 connected to the reception gain setting circuit 18 for setting the gain of the fax transmission signal to match the lines T and R and outputting the result. A transmission gain setting circuit 19 and each first terminal P1 is connected to the impedance matching and gain control circuit 13 and a second terminal P2 is connected to the PCM codec 14 and a third terminal. Analog switches 20 and 21 connected to the reception gain setting circuit 18 and switched by the first switching signal, and the first terminal P1 are connected to the impedance matching and gain control circuit 13. An analog switch connected to the PCM codec 14 and a third terminal P3 connected to the transmission gain setting circuit 19 and switched by the second switching signal. It consists of 22.

In the configuration of FIG. 1, the DC bypass circuit 11, the transformer 12, the impedance matching and gain control circuit 13 become the trunk circuit side of the private exchange, and the PCM codec 14 is for voice communication. .

Hereinafter, an operation example of FIG. 1 according to the present invention will be described in detail.

First, the analog switches 20-22 in FIG. 1 are initially in a state where the first terminal P1 and the second terminal P2 are connected. Therefore, when the analog voice signal is received from the lines T and R, the DC component is bypassed in the DC bypass circuit 11 of the trunk circuit of the private exchange. In addition, the impedance signal and the gain control are controlled through the transformer 12 and the impedance matching and gain control circuit 13 so that the voice signal is received by the PCM codec 14 through the analog switches 20 and 21, and the PCH digital voice data is received. The audio signal is converted into, and input to a speech processing circuit (not shown) to be processed so that the user can hear it. In addition, the voice data output from the voice data processing circuit by the user's voice is converted into a voice signal in the PCM codec 14, and the impedance matching and control of the trunk switching circuit of the private exchange through the analog switches 21 and 22 are performed. In circuit 13 and transformer 12, impedance matching and gain are controlled and transmitted over lines T and R.

On the other hand, when the user manipulates the reception or reception key for facsimile transmission and reception after completing a call with the other party, the switching control circuit 16 outputs the first and second switching signals under the control of the CPU 15. Accordingly, the analog switches 20-22 are connected to the first terminal P1 and the third terminal P3, respectively, so that facsimile transmission or reception is possible. In other words, the facsimile signal transmitted from the fax modem 17 in the transmission mode is set in the transmission gain setting circuit 19 so that the gain is set to the lie (T, R) side, and through the analog switch 22, the private exchange is performed. Impedance matching and gain are controlled in the impedance matching and gain control circuit 13 and the transformer 12 of the trunk circuit, and are transmitted through the DC bypass circuit 11 through the lines T and R. In the receiving mode, the facsimile signal received through the lines T and R transmits the direct current through the bypass signal 11, the transformer 12, and the impedance matching and gain control circuit 13. 21 is received by the reception gain setting circuit 18, and the gain is set in the reception gain setting circuit 18 in accordance with the fax modem 17 and received by the fax modem 17.

Therefore, the voice call and the facsimile can be controlled by switching the analog switches 20-22. In addition, when the user wants to make a voice call even in the state switched to the facsimile as described above, the voice call can be made by switching the analog switches 20-22 to the initial state under the control of the CPU 15.

2 is a detailed circuit diagram of one embodiment of the transmission and reception gain setting circuits 18 and 19 during the first step, and (a) is a concrete circuit diagram of the transmission gain setting circuit 18 and includes resistors R1 and R2. OPAM (Operational Ampilfier) (OP1) part feedback amplifier is connected to the output terminal of the fax modem 17 through the line 105, the level to attenuate the facsimile signal output from the fax modem 17 to a predetermined level Attenuation circuit 31, resistors R3, R4, and OP amplifier OP2 are configured as negative feedback amplifiers, which are connected to the output terminal of the level attenuation circuit 31, and amplify the attenuated signal levels. 32, resistors R5-R7, capacitors C1-C2, and OP amplifiers OP3 are configured as filters to be connected to the output terminal of the level amplifying circuit 32 to filter the amplified signals. Filter circuit 33 for removing noise, and resistors R8-R9 and OP amplifier OP4 are configured as negative feedback amplifiers. Connected to the output terminal of the filter circuit group 33, and to attenuate the level of the filtered signal consists of level attenuation circuit 34 to output to the analogue switch 22 via line 103. The

(b) is a detailed circuit diagram of the reception gain setting circuit 19. An inverting terminal (-) is connected to the analog switch 20 through a line 102 and a non-inverting terminal (+) is grounded so that the analog OR amplifier OP5 for inverting and amplifying the facsimile signal input through the switch 20, resistors R10-R11 and OP amplifier OP6 are configured as negative feedback amplifiers to output terminals of the OP amplifier OP5. A level attenuation circuit 41 connected to the analog switch 21 via a line 101 and mixing the output of the OP amplifier OP5 and the input signal through the analog switch 21 to attenuate it to a predetermined level; And resistors R12-R13 and OP amplifiers OP7 are connected to an output terminal of the level attenuation circuit 41 and amplify the attenuated signal level to an input terminal of the fax modem 17. And a level amplifier circuit 42 for inputting.

Hereinafter, an operation example of FIG. 2 according to the present invention will be described in detail. If the circuit of FIG. 1 is switched to facsimile and is in a transmission mode, the facsimile signal output from the fax modem 17 is input to the level attenuation circuit 31 of FIG. Therefore, the facsimile signal is attenuated to a predetermined level in the level attenuation circuit 31 and amplified back to the original level in the level amplifying circuit 32. After the noise is removed by filtering by the filter circuit 33 and then attenuated again by the level attenuation circuit 34, the gain is set in accordance with the line T and R side of FIG. It is output to the log switch 22. Therefore, the facsimile signal outputted to the fax modem 17 has noise removed and gain is set to match the line (T, R) side. In this case, the gain of + 5dB level on the fax modem 17 side should be set to 0dB or less on the line T and R side. This is achieved by adjusting the circuit constant value of the second circuit (a). .

On the other hand, when the circuit of FIG. 1 is in the facsimile reception mode, the other party's facsimile signal input through the lines T and R is inverted by the inverting terminal (-) of the OP amplifier OP5 of FIG. Inverted and amplified, the amplified signal is mixed with the facsimile signal input through the line 101 and attenuated to a predetermined level in the level attenuation circuit 41. The gain is set again in the level amplification circuit 42 and set in accordance with the fax modem 17 of FIG. 2 and input to the input terminal of the fax modem 17 through the line 104. Therefore, the gain is set to fit the receiving fax modem 17 as opposed to the transmission.

As described above, the present invention simplifies the circuit as a circuit in which a facsimile shares a direct current switch circuit, a transformer, an impedance matching, and a gain control circuit of a private exchange trunk circuit using an analog switch in a facsimile to which a private exchange is joined. There is an advantage in that the area occupied by the component can be reduced and can be easily controlled. In addition, by controlling the voice call and the facsimile using an analog switch, the voice call can be made even after the facsimile is completed.

Claims (1)

A transformer 12 for matching a DC bypass circuit 11 connected to the lines T and R to bypass DC, a public telephone network connected to the DC bypass circuit 11, and the transformer ( 12. A facsimile private exchange trunk circuit and a sharing circuit of a facsimile having an impedance matching and gain control circuit 13 connected to the input / output impedance and controlling gain, wherein the received analog voice signal is a digital PCM as voice data. The PCM codec 14 converts and outputs the input digital PCM voice data into an analog voice signal, and transmits the first and second switch signals under the control of the CPU 15 and the CPU 5 for controlling the system. A switching control circuit 16 for outputting a signal, a fax modem 17 for modulating a fax transmission / reception signal, and a fax modem 17 connected to set a gain of a received signal of the fax according to the fax modem 17; So And a transmission gain setting circuit 19 connected to the receiving gain setting circuit 18 and the fax modem 17 for setting and outputting a gain of a facsimile transmission signal according to the lines T and R, respectively. The first terminal P1 of is connected to the impedance matching and gain control circuit 13 and the second terminal P2 is connected to the PCM codec 14 so that the third terminal P3 is connected to the receiving gain setting circuit ( 18 and an analog switch 20, 21 connected by the first switching signal, and the first terminal P1 are connected to the impedance matching and gain control circuit 13, and the second terminal P2. ) Is connected to the PCM codec 14 and a third terminal (P3) is connected to the transmission gain setting circuit 19 is composed of an analog switch 22 which is switched by the second switching signal Facsimile private switching trunk and shared circuits.

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