KR920000093Y1 - Fax modem circuit - Google Patents

Abstract

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Description

FAX modem circuit with off hook detection device

1 is a circuit diagram of the present invention.

* Explanation of symbols for the main parts of the drawings

MICOM: MICOM MODEM: FAX MODEM

1: analog signal mixing unit 2: telephone line interface

3: ring signal detection unit 4: off-hook detection unit of the telephone

OP ₁ -OP ₂ : Amplifier PC ₁ PC ₂ : Photocoupler

T: Matching transformer SG: Surge observer

Ry: Relay Dz ₁ -Dz ₃ : Zener Diode

AND: Andgate

The present invention relates to a fax modem circuit for transmitting and receiving a document such as a text or picture using a microcomputer, and more particularly, to a fax modem circuit incorporating an off-hook detection device of a telephone.

In the conventional fax dedicated device, since the signal output from the modem IC is reflected back from the communication line and other circuits, an error occurs and the precise character or picture was not transmitted to the other party accurately. In order to solve this problem, in recent years, a technique for transmitting a document information to a counterpart so that a signal transmitted from a modem is not fed back to the modem has been developed. It had no function.

Therefore, the present invention is used when the telephone and the modem is shared on one telephone line when the modem is used after checking the off-hook of the telephone, and when using the telephone, the off-hook detection device of the telephone is used. To provide a built-in fax modem circuit.

The construction and operation effects of the present invention for achieving the above object will be described in detail with reference to the accompanying drawings.

1 is a fax modem (MODEM) connected to the MICOM of the present invention for transmitting and receiving necessary data, an analog signal mixing unit (1) for combining analog signals transmitted and received by a modem, and a telephone line. And a telephone line interface means (2) for converting a telephone function into a fax function and a telephone function by being connected to a telephone, and detecting a ring signal from a counterpart connected to a telephone line to detect a MICOM (MICOM). Ring interrupt signal Ring signal detection unit 3 for providing a frame and an off-hog detection unit 4 for detecting an off-hook state of the telephone.

The analog signal mixer 1 used in the present invention is an amplifier for comparing and amplifying analog data signals transmitted from the transmission terminal TXout of the modem MODEM and providing them to the telephone line interface 2 (OR _1). ) And an amplifier OP ₂ for comparatively amplifying the analog data signal that has passed through the interface 2 from the telephone line at the time of data reception and providing it to the receiving terminal RXin of the modem MODEM.

The inverting terminal of the amplifier OP ₁ operating during data transmission is connected to the transmission terminal TXout of the modem MODEM via a resistor R ₁ (R ₂ ) and a capacitor C ₁ , and the amplifier OP ₁ ) The capacitor C ₂ and the resistor R ₃ are connected in parallel between the inverting terminal and the output terminal of ₁ ), and the reference voltage is generated by dividing the DC voltage (+ Vcc) at the non-inverting terminal of the amplifier OP ₁ . The resistors R ₄ and R ₅ are connected, and the output terminal of the amplifier OP ₁ is connected with the capacitor C ₃ and the resistors R ₆ -R ₈ .

On the other hand, the inverting terminal of the amplifier OP ₂ operating at the reception of data is connected to the telephone line interface 2 via the resistor R ₉ , and a condenser is connected between the inverting terminal of the amplifier OP ₂ and the output terminal. (C ₃ ) and the resistor (R ₁₀ ) are connected in parallel, the capacitor (C ₄ ) is connected to the non-inverting terminal of the amplifier (OP ₂ ), and its output terminal is connected to the receiving terminal (RXin) of the modem (MODEM) It is connected.

In addition, the telephone line interface 2 used in the present invention provides an input analog signal to the receiving amplifier OP ₂ , and a matching transformer for transferring the transmission data output from the transmitting amplifier OP ₁ to the telephone line. (T) to configure the Zener diode (Dz ₁₎ (Dz ₂₎ of a matching circuit, a coil (L ₁₎ and switch (SW ₁₎ a to (SW ₂₎ a relay (Ry) and the relay (Ry) For the transistor Q ₁ .

On the other hand, the ring signal detection unit 3 detects the ring signal when the ring rings in the telephone and sends a ring interrupt (MICOM) to the MICOM. A photocoupler consisting of a capacitor (C ₆ ), a resistor (R ₁₁ ), a diode (D ₁ ), a zener diode (Dz ₃ ), a photo transistor (Qp ₁ ) and a photodiode (Dp ₁ ) to provide a signal. PC ₁ ) and AND gate (AND).

In addition, the off-hook detection unit 4 for detecting the off-hook state of the telephone is composed of a bridge diode (BD) and a photo coupler (PC ₂ ), the reference numeral SG in the figure is a sudden voltage change applied to the telephone line It is a surge observer to control and D ₂ indicates a relay protection diode.

The operation of the present invention configured as described above will be described in detail.

The present invention detects an off-hook state of a telephone by first checking whether the telephone is in use or not when a modem is to transmit computer data over a telephone line to a remote location. That is, when the phone is in the on-hook state, there is no output from the bridge diode (BD), so the photo coupler (PC ₂ ) is turned off and the interrupt input of the MICOM ( ) Or port (INψ) to recognize the status as on-hook, and the modem can perform the operation for transferring data.If it is off-hook, wait until the phone is on-hook and wait for the on-hook status. When the data is sent over the phone line.

Then, the modem (MODEM) is because the telephone line by the signal that has passed through the exit port (out) of a relay (Ry) the microcomputer (MICOM) when in use in the active state, and the switch (SW ₁₎ turned ON, and the switch (SW ₁ ) Is off, so the phone can no longer be used.

In addition, when a telephone signal is input from the outside when both the telephone and the modem do not use a telephone line, the modem is connected to the telephone line only when the ring signal detection unit 4 counts the number of rings to ring a predetermined number. If the user answers the telephone and picks up the phone while the modem is counting the number of rings (when it is in the OFF HOOK state), the modem stops counting the number of rings and enables the telephone call.

The operation of FIG. 1 circuit having the off-hook detection function of the telephone will be described in detail by dividing the operation into the process of receiving data and the process of transmitting data.

First, referring to the process of receiving data, the analog data signal input through the telephone line is adjusted to a uniform voltage by the surge observer SG, and then applied to the matching transformer T, and at the same time, the telephone and ring signal detector 3 ), The phone rings.

At this time, as the analog signal is applied to the capacitor C ₆ and the resistor R ₁₁ configured in the ring signal detector 3, the photodiode Dp ₁ operates to turn on the phototransistor Qp ₁ .

As the photo transistor Qp ₁ is turned on, a low signal is applied to the AND gate AND, and a low state signal is generated at an output terminal thereof to generate an interrupt terminal of the MICOM MICOM. ) Is entered.

The phone rings and the ring interrupt signal ( ) Is applied to the MICOM, the MICOM will generate a high hum signal through its output end when the telephone does not pick up until a predetermined number of times (e.g. 3 times) rings. It is applied to the base terminal of transistor Q ₁ via storage R ₁₂ .

As applied to a high-state signal to the base terminal is turned on and the transistor (Q ₁₎ coil (L ₁₎ has a bar which current flows, wherein the coil (L ₁₎ is the electromagnetic force due to a flow of current occurs switch (SW ₁ ) Turn on.

When the switch SW ₁ is activated, the switch SW ₂ is turned off so that a ring signal is no longer provided to the telephone and the telephone function is switched to the fax function.

Accordingly, the analog data signal input to the matching transformer T through the telephone line is adjusted to a predetermined voltage by the matching transformer T and then connected to the inverting terminal of the receiving amplifier OP ₂ via the resistor R ₉ . Is entered.

When a signal having a predetermined voltage level is input, the amplifier OP ₂ comparatively amplifies the input signal and inputs it to the receiving terminal RXin of the modem MODEM.

When the analog data signal is input to the receiving terminal (RXin), the modem (MODEM) is connected to the interrupt request terminal ( ) To let MICOM start receiving data.

Interrupt request signal from the modem (MODEM) ) Is authorized, MICOM issues a command to receive data over the data bus.

At this time, the modem MODEM generates an address signal, converts the input analog data signal into a digital data signal, and provides the converted digital data signal to the MICOM through the data bus.

On the other hand, when there is no data received, the modem MODEM indicates an interrupt request signal indicating this fact. Withdraw and notify MICOM. The microcomputer MICOM then turns off the transistor Q ₁ by providing a low hook signal to the transistor Q ₁ through its output terminal out.

As the transistor Q ₁ is turned off, no current flows in the coil L ₁ so that the switch SW ₁ is turned off and the switch SW ₂ is turned on so that no further data is received.

Meanwhile, referring to a process of transmitting data, first, the microcomputer MICOM applies the data to be transmitted to the transistor Q ₁ through the output terminal out of a hook signal having a high tlf state on the data bus.

At this time, the transistor Q ₁ is turned on so that a current flows in the coil L _{1. When} a current flows in the coil L ₁ , the switch SW ₁ is turned on and the switch SW ₂ is turned off.

In this state, the modem MODEM converts the digital data signal inputted through the data bus into an analog signal and converts the converted signal through the transmission terminal TXout to the inverting terminal of the transmission amplifier OP ₁ . To apply.

At this time, the amplifier OP ₁ sets the level of the input signal to the reference voltage (R ₄ ) by the resistor R ₄ (R ₅ ). Amplify and compare to) and apply to matching transformer (T) via capacitor (C ₃ ) and resistor (R ₆ ).

The transmission data signal applied to the matching transformer T is transmitted to the other party's fax machine (not shown) through the telephone line.

If all the data to be transmitted has been transmitted, the modem will not accept the interrupt request terminal ( You will be notified to MICOM.

At this time, the microcomputer MICOM outputs a low hook signal from the output terminal thereof to the transistor Q _1. At this time, the switch SW ₁ is turned off, the switch SW ₂ is turned on, and the system is first turned on. Returns to the state (ie no phone or modem).

The present invention, which operates in this way, not only feeds the document information back to the modem because it is not fed back to the modem, but also has the off hook detection function of the telephone. will be.

Claims (1)

It handles the fax modem (MODEM) connected to MICOM and transmits and receives the necessary data, and processes the signal transmitted from the above modem modem (MODEM), and provides the signal inputted through the telephone line to the modem modem (MODEM). An analog signal combination unit 1, a telephone line interface 2 connected to a telephone line and a telephone to convert a telephone function into a fax function, and a telephone function into a telephone function, and a ring signal connected to the telephone line to detect a ring signal In the fax modem circuit provided with the detector (3); The off-hook detection unit 4 of the telephone for detecting the off-hook state of the telephone, including a bridge diode BD connected to the telephone, and a photo coupler PC ₂ composed of a photodiode DP ₂ and a phototransistor QP ₂ . Fax modem circuit with a built-in off-hook detection device of the telephone, characterized in that it comprises a).