JPH05268379A - Modem - Google Patents

Abstract

PURPOSE:To make the entire MODEM thin in its profile and to accommodate the MODEM to an IC card or a thin profile portable computer. CONSTITUTION:A MODEM interface 14 connecting to a terminal equipment in a MODEM 1 used to make data communication between terminal equipments through a telephone line is provided with photocoupler elements 14',14' giving/ receiving a signal between the terminal equipment 15 and the MODEM 1. Then the power supply of the MODEM 1 and the terminal equipment 15 is isolated by the photocoupler elements 14',14'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modem device (hereinafter abbreviated as a modem) for performing data communication using a telephone line.

Miniaturization and thinning of portable personal computers, word processors and the like are being advanced. on the other hand,
Data communication in which data is transferred between computers using a telephone line has become widespread.

In such data communication, a modem for converting a digital signal into an analog signal and transmitting it to a telephone line, and receiving an analog signal from the telephone line and converting it into a digital signal is a telephone line and a computer (hereinafter referred to as a terminal). It is necessary to separate it from the device in terms of direct current (the conditions for separation are the withstand voltage DC voltage of 250 V or more according to Japanese regulations,
Insulation resistance is defined as 0.2 MΩ).

Therefore, the conventional modem uses a line transformer to perform direct current separation between the telephone line and the terminal device. The line transformer is a large part, and parts such as a capacitor are also large in size because they require a large withstand voltage because of the above DC separation conditions. Therefore, conventional modems are large and cannot be thinned, and the entire modem is integrated into an IC.
It could not be built into a card.

[0005]

2. Description of the Related Art FIG. 4 shows the configuration of a conventional modem device.
In the figure, 100 is a modem device, and 101 is an input protection element, which protects against a high-voltage shock voltage due to lightning or the like. Reference numeral 102 denotes a polarity matching diode, which is composed of a diode bridge and ensures that the polarity of the DC voltage applied to the modem is always in a fixed direction even when the polarity of the DC voltage of the telephone line is reversed. .. An off-hook / dialing circuit 103 detects an off-hook and outputs a dial signal. Reference numeral 104 denotes a ring detection circuit, which is composed of a photocoupler and detects a calling signal. A photocoupler 105 optically detects a calling signal. Reference numeral 106 is a pseudo-inductance circuit, which bypasses the direct current from the telephone line. C2 and C3 are coupling capacitors, which cut off DC current and allow AC signals to pass through. Reference numeral 107 is a line transformer that separates the telephone line from the terminal device side in terms of direct current and transmits an alternating current signal. A DC / DC converter 108 shifts the DC voltage of the telephone line and supplies it to the modulation / demodulation unit 110 as a power supply voltage. Reference numeral 109 is a transformer for separating the terminal device from the telephone line in terms of direct current. A modulation / demodulation unit 110 modulates a digital signal of the terminal device into an analog signal and demodulates the analog signal transmitted from the telephone line into a digital signal.
111 is a terminal device.

In the configuration shown in the figure, when there is a call from the other party, the ring detection circuit 104 operates, the call signal is detected by the photocoupler 105, and the modulator / demodulator 11
Input is notified to 0.

Further, the pseudo-inductance circuit 106 bypasses the direct current from the telephone line and allows it to flow. That is, the DC voltage is divided by the resistors R1 and R2 and becomes the bias voltage of the transistors TR1 and TR2 connected in Darling mode.
The capacitor C1 prevents the bias voltage of TR1 from changing due to the AC component. A substantially constant direct current is caused to flow from the collector side to the emitter side of TR1 and TR2 regardless of the magnitude of the AC component. And the capacitor C2
The DC current is cut off by C3, the DC current does not flow in the line transformer 107, and only the AC signal is input to the line transformer 107 and transmitted to the modulation / demodulation unit 110.

The transmission signal converted from a digital signal to an analog signal by the modulator / demodulator 107 is sent to the telephone line via the line transformer 107, capacitors C2 and C3, and the pseudo inductance circuit 106.

On the other hand, the DC / DC converter 108 performs DC / DC conversion of the DC voltage from the telephone line and the modulator / demodulator 11
Supply to 0. A transformer 109 is inserted in the DC / DC converter 108 in order to guarantee the direct current separation between the telephone line and the terminal device.

The off-hook / dialing 103 is composed of a photo coupler or the like, detects an off-hook signal, and sends a dial signal.

[0011]

As described above, the conventional modem requires the line transformer. The line transformer was a large component and required a height of about 10 mm. Therefore, conventionally, it was impossible to fit the entire modem including the transformer into the IC card.

An object of the present invention is to reduce the thickness of the entire modem so that the modem can be stored in an IC card or a thin portable computer.

[0013]

According to the present invention, a modem and a terminal device are coupled by a photocoupler, a signal is transmitted between the terminal device and a modulation / demodulation unit of a tem by a photocoupler, and a transformer is used. Instead, the terminal device and the telephone line are separated from each other in a direct current manner (separation of the power supply unit).

Therefore, since it is not necessary to separate the modem and the telephone line in the ring detection circuit and the polarity detection circuit in terms of direct current, it is possible to reduce the number of photocouplers by using the voltage detection by the resistance and the protection diode. did. In addition, the function of the conventional line transformer was realized by a differential circuit, and it was possible to match the transfer of analog signals between the telephone line and the modulator / demodulator without using the line transformer. Also, in the DC / DC converter, it is not necessary to separate the telephone line from the terminal device in terms of direct current. Therefore, the transformer of the DC / DC converter is not used, and the modem device does not include any transformer. ..

FIG. 1 shows the basic configuration of the present invention. In the figure, 1 is a modem device, and 2 is a polarity matching diode circuit, which comprises a diode bridge. Reference numeral 3 denotes a ring detection circuit, which is composed of voltage dividing resistors Ra and Rb, and detects the calling of the other party by the divided voltage. Reference numeral 4 is a dialing circuit, 5 is a pseudo-inductance circuit, and 6 is an AC signal transmission circuit, which is configured by an active circuit having a transformer function without using a transformer, and transmits an analog signal between the telephone line and the modulation / demodulation unit 7. It is something to do. A modulator / demodulator 7 demodulates an analog signal into a digital signal and modulates a digital signal into an analog signal. Reference numeral 8 is a polarity detection circuit, which detects the reversal of the polarity of the telephone line by the voltage dividing resistors (Ra, Rb). Reference numeral 9 denotes a DC / DC converter for DC / DC converting the DC voltage of the telephone line and supplying it as the power supply voltage of the modulation / demodulation unit 7. Reference numeral 11 denotes a power supply unit which supplies a power supply voltage to the modulation / demodulation unit 7 when the modem and the telephone line are not connected.
Reference numeral 12 denotes a power source switching unit, which is a power source unit (battery) 11
And the DC / DC converter 9 are selected to switch the power supply. Reference numeral 14 is a modem interface for exchanging signals with the modulation / demodulation unit 7 and the terminal device by an optical coupling element (photocoupler). 14, 1
4'is an optical coupling element (hereinafter referred to as a photo coupler),
Reference numeral 15 is a terminal device, and 16 is a terminal device interface.

[0016]

The operation of the configuration shown in FIG. 1 will be described. The operation of the configuration shown in the figure will be described.

The polarity matching diode circuit 2 prevents the direction of the DC voltage applied to the modem from changing even if the polarity of the DC voltage on the telephone line is reversed. When called by the other party, a divided voltage is generated in the voltage dividing resistors R1 and R2 of the ring detection circuit 3 and is input to the ring voltage input terminal (RING) of the modulation / demodulation unit 7. Protection diode circuit 1
Reference numeral 3 protects the input of the ring voltage input terminal (RING) so that a voltage higher than 5 V is not input.

The DC / DC converter 9 converts DC voltage from the telephone line into DC / DC. Then, the power supply switching unit 12 detects the off-hook signal (OH) of the modulation / demodulation unit 7, and switches the power supply to the modulation / demodulation unit 7 from the power supply unit (battery) to the DC / DC converter 9 by off-hook.

The AC signal transmission circuit 6 is composed of a coupling capacitor for blocking a DC current from the telephone line and passing an AC signal, and a differential circuit, and converts a balanced signal from the telephone line into an unbalanced signal. Further, the unbalanced signal from the modulation / demodulation unit 7 is converted into a balanced signal and sent to the telephone lines L1 and L2 (details of the AC signal transmission circuit will be described later).

The modem interface 14 is used for the terminal device 1.
The signal from 5 and the signal from the modulator / demodulator 7 are transferred. The optical coupling element 14 '(photocoupler) is a modulator / demodulator 7
To transmit to the terminal device 15. The optical coupling element 14 ″ also transmits the signal from the terminal device 15 to the modulation / demodulation unit 7.

The modulation / demodulation unit 7 converts the transmission digital signal of the terminal device 15 into an analog signal and sends it to the AC signal transmission circuit 6. Further, the modulation / demodulation unit 7 inputs the received analog signal output from the AC signal transmission circuit 6, converts it into a digital signal, and sends it to the terminal device 15 via the modem interface 14.

Further, according to the present invention, since the modem 15 separates the terminal device 15 from the modem in a direct current manner, the polarity detection circuit 8 also divides the voltage dividing resistors Rc and Rd.
It can be configured by. That is, the polarity detection circuit 8 detects the change in the polarity of the DC voltage of the telephone line by detecting the change in the divided voltage generated in the voltage dividing resistors Rc and Rd (refer to CCITT Recommendation V.22bis. In the personal computer communication, since the response of the other party is performed by sending a signal from the other party, the polarity detection circuit 8 is not always necessary).

In the structure of FIG. 1, the dialing circuit 4 and the pseudo-inductance circuit 5 have the same structure as the conventional circuit, and the description thereof will be omitted. According to the present invention, the terminal device and the modem device are coupled by the optical coupling elements 14 'and 14 ", and the modem and the terminal device are completely separated from each other in terms of direct current. It is not necessary to have legal requirements for power supply separation (withstand voltage of 250 V or more for DC and telephone line and terminal device for DC and insulation resistance of 0.2 MΩ or more) in the circuit portion of the modem, so the polarity detection circuit 8 and the ring detection circuit are provided. 3 resistance (R
a, Rb and Rc, Rd) and the protection diode circuit 13
It is possible to eliminate the need for a photocoupler, which was required in the past. In FIG. 1, the protection diode circuit 13 for keeping the output voltage of the polarity detection circuit 8 within a certain range is not shown. Further, the transformer which has been conventionally required for the DC / DC converter 9 can be eliminated for the same reason. Further, in connection with the AC signal of the telephone line and the modulation / demodulation unit 7, the line transformer can be eliminated by the AC signal transmission circuit 6 having the conventional transformer function composed of the differential circuit and the capacitor, and the entire modem is stored in the IC card. It will be possible.

[0024]

Embodiments of the present invention will be described with reference to FIGS. Reference numerals B, C, D, E, FH, and I in FIG. 2 indicate that they are connected to the same reference numerals in FIG.

In FIG. 2, reference numeral 20 denotes an input protection element for protecting the modem device from a shocking high voltage such as lightning strike. Reference numeral 21 is a diode bridge, which is a polarity matching diode circuit. Reference numeral 22 is a ring detection circuit, which is composed of voltage dividing resistors R1 and R2.
B1 is a buffer for inputting the ring detection voltage to the modulation / demodulation unit 32. Reference numeral 23 is a protection diode circuit for protection by the buffer B1, which is composed of diodes D1 and D2. 24 is a dialing circuit,
It outputs a dial signal and is constituted by a photo MOS relay 24 '. Reference numeral 25 is a pseudo inductance circuit, 26 is a DC / DC converter, 27 is a battery, and 28 is a power supply switching unit. Reference numeral 29 is a polarity detection circuit, which is composed of voltage dividing resistors R4, R5, R6 and R7 for detecting the polarity of the polarity detection voltage on the telephone line. The diodes D3, D4, D5, D6 are diodes for keeping the polarity detection voltage within a certain range and for protecting the buffers B2, B3 (described later). B2 and B3 are buffers for inputting the polarity detection voltage to the modulation / demodulation unit 32.

In FIG. 3, 30 is an AC signal transmission circuit,
Reference numeral 31 is a differential circuit A, and 31 'is an operational amplifier (OP1). 32 is a differential circuit B, 32 'and 32 "are operational amplifiers (OP2 and OP3). C10 and C12 are capacitors, D10 is an input protection element, D11 and D12 are input protection diodes, and operational amplifiers 31' and 32 are provided. ', 3
It protects the 2 "from an excessive input voltage. The resistor R15 prevents the transmission signal from the terminal device from being recursively input to the terminal device.

Reference numeral 32 is a modulator / demodulator, and 33 is a modem interface. Reference numerals 40, 41, 42, 43, 44 and 45 are photocouplers. In the symbols representing terminals of the modulation / demodulation unit, L1 and L2 are analog signal output terminals of the modulation / demodulation unit, V
CC is a power supply input terminal, GND is a ground terminal, and * OH is an off-hook signal output terminal, which is turned on by off-hook and turned off by on-hook (* represents negative logic. The same applies hereafter). * RING is a ring signal input terminal. * RVS1 and * RVS2 are polarity detection voltage input terminals. * ER (Equipment Lady)
Is an input terminal of a receivable signal on the terminal device side. * RS
(Request to send) is an input terminal for a signal indicating a transmission request from the terminal device. SD is an input terminal for a transmission signal from the terminal device. RD is an output terminal for receiving signals from the telephone line. * CS (Clear to Send) is an output terminal of a transmission enable signal to the terminal device. * D
R (data set ready) is an output terminal of a signal for notifying the terminal device that the modem is ready.

The symbols of the signals input to and output from the modem interface 33 have the same meaning as in the description of the terminals of the modem unit 32. The operation of the configuration shown in FIGS. 2 and 3 will be described.

In the case of dialing, * OH is turned on by an instruction from the terminal device, and the dialing circuit 24 sends a dial signal to the telephone line L via the photomos relay 24 '.
1 and output to L2.

In the case of dialing by another method, * OH is turned on, and then the DTMF signal is output from the modem unit to the telephone lines L1 and L2. The operation of the ring detection circuit 22 in FIG. 2 will be described.

When a ring voltage is input from the telephone line, a maximum of 83 Vrms (1
An AC signal of 6 Hz) is applied. The voltage is the resistance R
The voltage is divided by 1 and R2, a voltage of 0 to 5 V is taken out, and the voltage range is guaranteed by the diodes D1 and D2. Then, the ring signal input terminal * RI of the modulation / demodulation unit 32 is passed through the buffer B1.
Input to NG.

Next, the operation of the polarity detection circuit 29 will be described.
If the polarity of the telephone line is reversed in the exchange, L1,
The potential difference between L2 changes from + 48V to -48V. The voltage change is taken out by the voltage dividing resistors R3, R4, R5, R6, and the voltage range is guaranteed by the protection diodes D3, D4, D5, D6, and then the modulation / demodulation unit 3 via the buffers B2, B3.
2 polarity detection voltage input terminals * RVS1 and * RVS2.

The voltage dividing resistor R of the ring detection circuit 22
1, R2, and voltage dividing resistors R3, R of the polarity detection circuit 29
4, R5 and R6 should be large enough to satisfy the standard of the telephone line.

The operations of the DC / DC converter 26 and the power supply switching unit 28 are as described in FIG. The operations of the input protection element 20, the diode bridge 21, and the pseudo inductance circuit 25 are the same as those of the circuit shown in FIG.

Modem interface 33 and modulator / demodulator 32
The operation will be described. When the terminal device transmits data, a signal (* ER) indicating that the terminal device is ready is sent from the terminal device and input to the modulation / demodulation unit 32 via the photocoupler 40.

The modulation / demodulation unit 32 sends a signal data set ready (* DR) indicating that the modem is ready to the terminal device via the photo coupler 45. The terminal device sends a transmission request signal (* RS). *
The RS is input to the modulation / demodulation unit 32 via the photo coupler 41. The modem which receives this sends the carrier wave to the telephone line. The receiving modem (not shown) detects that the carry is transmitting data.

The modem sends out a send enable (CS) to the terminal device. The CS is transmitted to the terminal device via the photo coupler 44. When the terminal device receives the transmission enable (CS) from the modulation / demodulation unit 32, it transmits the transmission data (SD). The transmission data (SD) is sent to the modulation / demodulation unit 32 via the photo coupler 42.
Is input to, converted to an analog signal and sent to the telephone line.

When receiving the data from the telephone line, the modulation / demodulation unit 32 converts the received analog signal into a digital signal and converts the received data (RD) into the photo coupler 4.
3 to the terminal device.

Next, the operation of the AC signal transmission circuit 30 will be described. (1) Operation during reception. In the telephone line, the polarities of the signals passing through the capacitors C10 and C12 are opposite because they are considered to be substantially balanced transmission. Therefore, for example, it is assumed that when the transmission signal a passes through the capacitor C10 as illustrated, the signal b is output from the capacitor C12 as illustrated. The output of the operational amplifier 31 'is used as the signal c.

The signal a is input to the non-inverting input terminal of the operational amplifier 31 'and used as a reference voltage. The signal b is the operational amplifier 24
Input to the inverting input terminal of. As a result, the inverted signal c of the signal b is output and input to the modulator / demodulator 32 as an unbalanced signal.

(2) Operation during transmission It is assumed that the transmission signal is the signal d shown in the figure. The transmission signal d is input to the non-inverting input terminal of the operational amplifier 32 '. As a result, the operational amplifier 32 'outputs the signal e in phase with the signal d. Furthermore, since the output signal e of the operational amplifier 32 'is input to the inverting input terminal of the operational amplifier 32 ", the operational amplifier 32" outputs the inverted signal f of the signal d.
Then, the signals e and f are output as balanced signals to the telephone line via the capacitor C2 and the pseudo inductance circuit 25.

Further, the transmission signal f is input to the operational amplifier 31 'by the resistor R15, and recursively, the operational amplifier 31'.
Output from. In the above description, in the modem interface 33, if the photo coupler is connected to the terminal device and the signal is not separated in terms of direct current, the capacitors C10 and C12 are required to maintain the direct current voltage 25 in accordance with the legal requirement.
It is necessary to have an insulation resistance of 0.2 MΩ or more at 0V. Therefore, the capacitors C1 and C2 have a high withstand voltage and a large shape. However, when the capacitors C1 and C2 are coupled by a photocoupler as in the present invention, the capacitors C1 and C2 have a withstand voltage substantially withstanding the DC voltage of the telephone line. If it can be done, it can be made smaller.

As described above, the modem device of the present invention does not include a transformer, a relatively large photo coupler can be minimized, and the coupling capacitor can be miniaturized.

[0044]

Since the modem of the present invention does not include a transformer such as a line transformer and has no portion connected to the power source portion of the terminal device, it is not necessary to consider the withstand voltage against the voltage of the power source portion. Therefore, each part of the modem circuit can be downsized, and the entire modem can be accommodated in the IC card.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 shows an embodiment (1) of the present invention.

FIG. 3 shows an embodiment (2) of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional modem device.

[Explanation of symbols]

 1: Modem device 2: Polarity matching diode circuit 3: Ring detection circuit 4: Dialing circuit 5: Pseudo-inductance circuit 6: AC signal transmission circuit 7: Modulation / demodulation unit 8: Polarity detection circuit 9: DC / DC converter 11: Power supply unit (Battery) 12: Power supply switching unit 13: Protection diode circuit 14: Modem interface 15: Terminal device 16: Terminal device interface

Claims (6)

[Claims] 1. A modem device for performing data communication between terminal devices via a telephone line, wherein a modem interface (14) of a modem device (1) connected to the terminal device comprises a terminal device (15) and a modem device (1). The modem device (1) and the terminal device (15) are provided with an optical coupling element (14) ', (14) "for optically transmitting and receiving a signal between the modem device (1) and the terminal device (15).
4) ', (14) "The power supply is separated by the modem device. 2. The modem device according to claim 1, comprising a ring detection circuit (3) for detecting a calling signal from the other side, and the ring detection circuit (3) is a resistance voltage dividing circuit for dividing the voltage from the telephone line. A modem device characterized by being constituted by. 3. The modem device (1) according to claim 1 or 2, further comprising a polarity detection circuit (8) for detecting the inversion of the polarity of the DC voltage of the telephone line, and the polarity detection circuit (8) is connected to the telephone line. A modem device comprising a resistance voltage dividing circuit for dividing a voltage. 4. The DC / DC converter according to claim 1, 2 or 3 for extracting a DC voltage from a telephone line and shifting the voltage.
Power the DC converter (9) and the modem device (1) to the DC
Output from the DC / DC converter and the power supply of the modem device (1)
(11) Power output switching section to select and switch between output
(12) and a modem device by detecting an off-hook signal
A modem device characterized in that the power supplied to (1) is switched to the output from the DC / DC converter (9). 5. The method according to claim 1, 2, 3 or 4,
An AC signal transmission circuit that configures the circuit that bypasses the DC current from the telephone line of the modem device with a pseudo-inductance circuit (5) that does not include a transformer and transmits the AC signal from the telephone line to the modem unit (7) of the modem device. A modem device in which (6) is configured by an active circuit not including a transformer. 6. The modem device according to claim 1, 2, 3, 4, or 5, wherein the modem device (1) does not include a transformer and is built in an IC card.