JPS603256A - State control system of modem - Google Patents

Abstract

PURPOSE:To improve the fluctuation of level of a voice signal by controlling the output level of an MODEM an impedance and a balancing network by the state information of a terminal device connected to the identical line with the MODEM. CONSTITUTION:An output of the MODEM 1 is supplied to an amplifier 2 via a parallel circuit comprising a resistor R1 and a switch SW1; and the output of the amplifier 2 is connected to an unbalancing/balancing converting circuit 3. Outputs X, Y of the converting circuit 3 is connected respectively to terminals A, B of a telephone line via a parallel circuit comprising a resistor R6 and a switch SW2. A parallel circuit comprising resistors R8, R9 and switches SW4, SW5 is connected between the outputs Y, X of the converting circuit 3 and inputs C, D of a balancing/unbalancing converting circuit 4, and further a switching circuit of balancing networks Z1, Z2 is connected between both the lines. Then each switch is controlled for changeover by a relay 9 connected to a terminal device 8 to change the amplification factor of the MODEM and also change the impedance of the input/output impedances and the balancing network circuits.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for controlling the electrical characteristics of a modem connected to the same line as a terminal device using status information of the terminal device.

Conventionally, data transmission systems using telephone lines and the like have been developed and put into practice.

First, the configuration of the modem circuit used in this system will be explained with reference to the drawings, and its drawbacks will be mentioned.

FIG. 1 is a block diagram showing a conventional modem circuit using a telephone line.

The transmitted digital signal is converted into a binary frequency signal by a modulation circuit 1, amplified by an amplifier 2 including resistors R2 and R3, and then converted into a balanced signal by an unbalanced/balanced conversion circuit 3 in the next stage. The signal is passed through resistor R4 and filter 5 and sent to terminals A and B for connection to a telephone line (not shown).

On the other hand, in the case of reception, the binary frequency signal that has reached the telephone line A and B terminals is converted into an unbalanced signal by the balanced/unbalanced conversion circuit 4, which passes through the resistance ratio 12, 3, and then the next stage resistor R. .

In the figure, resistors R4, R5, inserted on the transmitting and receiving sides,
12, n 13 and the resistor group inserted between them (11% R14% Rxs) and the balance net circuit Z1 form a hybrid circuit, and these values are set in advance. It is set to a fixed value.

However, due to the input impedance fluctuation of the telephone 8 caused by the on/off hook state of the telephone hook 8, the voice signal 7
This had the disadvantage that the output level of the bell modem fluctuated and the hybrid circuit became unbalanced, causing transmitted data No. 8 to leak to the receiving side of the modem, causing malfunctions.

An object of the present invention is to provide a modem that solves the above-mentioned drawbacks and allows the modem to operate stably by controlling the state information of the terminal equipment connected to the same line as the modem, the output level input impedance of the modem, and the balance net. To provide a state control method 1. In order to achieve the above object, the modem state control method according to the present invention connects a relay to a terminal device whose input impedance changes by a certain operation, A first switch is connected in parallel to a resistor that changes the amplification degree of an amplifier that amplifies the modulated output of the modem connected to the same line, and nine unbalanced/balanced circuits are inserted on the transmitting side and the receiving side, respectively. A second switch is connected in parallel to some of the resistors of the resistor group inserted between the balanced/unbalanced circuit and the line connection terminal, and an impedance element of the balance net circuit is further inserted between the resistor group. When two switches are connected to these two impedance elements and the above-mentioned certain operation is performed,
By controlling on/off and switching of the first, second, and third switches by the relay, the amplification degree of the modem is changed, input/output impedance elements are changed, and the impedance value of the balance net circuit is changed. It is configured as follows.

According to the above configuration, the output level and the audio level of the modem can always be kept constant regardless of the status of the terminal equipment, and the amount of data signals transmitted by the modem that go around to the receiving side is also significantly reduced. The object of the invention is fully achieved.

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

2U is a circuit diagram showing an embodiment of the /ζ modem circuit to which the method of the present invention is applied.

Amplifier circuit 2 including variable 11/4 circuit 1, resistance ratio 2, and R3
In between, a parallel circuit of an amplifier gain selection switch SW1, which is a first switch, and a resistor R1 is inserted, and an unbalanced/balanced conversion circuit 3 is connected to the output terminal of the amplifier 2.

One end of a resistor R4 is connected to the X point of the balanced output of the unbalanced/balanced conversion circuit 3, and one end of a parallel circuit of a resistor R6 and a switch SW2 is connected to the other end of the resistor R4.
Connect the other end of the parallel circuit to telephone line terminal A.

On the other hand, one end of the resistor R5 is connected to the Y point of the balanced output of the unbalanced/balanced conversion circuit 3, and one end of the parallel circuit of the resistance ratio 7 and the switch SWa is connected to the other end of the resistance ratio 5, and the parallel circuit Connect the other end to telephone line terminal B.

Connect one end of the parallel circuit of the resistance ratio 8 and the switch SW4 to the Y point of the unbalanced/balanced conversion circuit 3,
The other end of the parallel circuit is connected to one end of a series circuit with a resistance ratio of 1o and R114, and the other end of the series circuit is connected to the input terminal C of the balance/unbalance conversion circuit 4.

Balanced output X of unbalanced/balanced conversion circuit 3
Similarly to the above, a parallel circuit of a resistor R9 and a switch SWs, a resistor R11, and a resistor 1 (, 15) are connected in this order to the input terminal of the balance/unbalance conversion circuit 4.

The /ξ switches 8W2 to SWs provided in the resistor groups R4 to R15 (including the later-described resistor 12 and Rta) correspond to second switches.

Furthermore, resistors R,, and 1 (connect the connection point of 115 and the third switch SWeΩ common terminal), and insert the balance wire Zl between the contact E of switch 8W6 and the connection point of resistance ratio 10 and UX4. , similarly inserted between the contact F of the balance net Z2 and the connection point of the resistors RIIO and Rt4.

Next, on the receiving side, a resistance ratio of 12 is inserted between the input terminal C of the dobalance/unbalance conversion circuit 4, which is the connection point between the telephone line A terminal and the resistor 1, and the resistance ratio is similarly balanced with the connection point between the telephone line S terminal and the resistor 1. - Insert a resistance ratio of 3 between the input terminals of the unbalanced conversion circuit 4. Furthermore, a resistor Rte, EL17 is connected to the output terminal of the balanced/unbalanced conversion circuit 4.
Connect one end of the amplifier 5 including ij L/, and connect the output terminal of the amplifier 5 to the input terminal of the temporary DD circuit 60. Take out three output terminals from the telephone 8, and connect L to the output terminal, respectively'..., Connect to speech lines A and B, and connect the S terminal to the input terminal of the relay circuit 7 in the modem. The output of the relay circuit 7 is configured to drive each switch SW] to SW6.

Next, the operation of this modem circuit will be explained.

When telephone 8 is on-hook, switch SWl is off and switches SW2 to SW5IVv5 are on and balanced.)7
．． As for 1Z2, Zl having high impedance is selected by switch SW6. When , the impedance of the telephone line A1S terminal is as follows, since the telephone 8 is on-hook.
It has high impedance. In this state, the transmitted digital signal is converted into a binary frequency signal by the 61 circuit 1, amplified by the amplifier 2 including 1 resistor 1, f'2, and R3, and converted into a balanced signal by the unbalanced/balanced conversion circuit 3. Afterwards, it passes through resistors R41, 11, 5 and switches SW2 and SW3 to the telephone circuit, 17&, S
sent to the terminal.

In the case of reception, the binary frequency signal arriving at the telephone line A and B terminals passes through resistors J2 and R13, is converted into an unbalanced signal by the balanced/unbalanced conversion circuit 4, and is converted into an unbalanced signal by the resistors R,..., 几1.
7 is amplified by the amplifier 5, input to the demodulation circuit 6, and output as a digital signal.

Next, when the telephone 8 is off-hook, the switch S Wl is on, the switches S Wz to S Ws are off, and Z2, which has a low impedance, is selected as the balance net.

At this time, the impedance of the input terminal, ijμA, and B terminal is 'I6. . Since Fiiso S is off-knock, it has low impedance.

In this state, the transmitted digital signal has a modulation frequency of 1
It is converted into a binary frequency signal by ・Switch S bacteria 11
It is amplified by the amplifier 2 including the stiffness resistors J, 14, and t'L3, and -i1'-+ is output by the unbalanced/balanced conversion circuit 3.
'After being converted into an equilibrium signal, resistors R4, R6 and R5,1
11i telephone line & is sent to the B terminal.

Is the reception “easiness” “Yama 2 F+”? The binary frequency σ that reached the 13th terminal of the 1st line A (Number 16 is a resistance) is also 12%' R
13 is converted into an unbalanced signal by a 1-balance 7-balance conversion circuit 4, and then a 1-resistor IF61. t is also amplified by the amplifier 5 including 17, inputted to the 1 counterclaim circuit 6, and outputted as a digital signal.

Generally, when telephone 8 goes on-hook, telephone line A
The impedance between telephone lines A and B is not high, but when the telephone line goes off-hook, the impedance between telephone lines A and B becomes low.

When the telephone 8 is on-hook, the switch SW of this circuit
1 is turned off and the gain of amplifier 2 is lowered, and when off-hook, the switch SWI is turned on and the gain of amplifier 2 is increased to compensate for the output level fluctuation due to the above-mentioned circuit impedance fluctuation, so the output level can be stabilized. I can figure it out.

When phone 8 is on-hook, switch 8-92-5
When w5ffi is on and off hook, switch 8 W2
~ SW5 is turned off to switch the modem's human output impedance to stabilize the parallel impedance of the telephone and modem as seen from the line side when on and off-hook.

Further, when on-hook, the switch SWe selects Zl, which has a high impedance of the balance net, and when off-hook, selects Z2, which has low impedance, to prevent the amount of looping from the sending side to the receiving side in the modem.

As explained in detail above, according to the present invention, status information of terminal equipment connected to the same line, for example, whether a telephone is turned on,
By controlling the modem's output level, input/output impedance, and balance network using off-hook information, it is possible to improve audio signal level fluctuations and modem output level fluctuations, and to optimize the balance network. ;・ml included! I'
! F. It has the effect of improving sex.

[Brief explanation of drawings]

Figure 11 is a block diagram showing the configuration of a conventional modem circuit, and Figure 2 1d is an implementation of a modem circuit according to the present invention.
FIG. ■... Variable J, IL, Q circuit 2.5... Amplifier (amplifier) 3... Unbalanced/balanced conversion circuit 4... Balanced/unbalanced conversion circuit 6... Demodulation circuit 7...
・Relay 8 ... Electric power supply 11 sw, -sw, ... Switch 1% R17 ... Resistor Z1% Z2 ... Balance net patent applicant NEC Corporation patent applicant Nippon Telegraph and Telephone Public corporation agent Patent attorney Hisashi Inoro

Claims (1)

[Claims] A relay is connected to a terminal device whose input impedance changes due to a certain operation, and a relay is connected in parallel to a resistor that changes the amplification degree of an amplifier that amplifies the modulated output of a modem connected to the same line of this terminal device. Connect the switch of
A second switch is connected in parallel to some of the resistors of the resistor group inserted between the unbalanced/balanced circuit and the line connection terminal of the unbalanced/balanced circuit inserted on the transmitting side and the receiving side, respectively, and The impedance element of the balance net circuit inserted between the resistor groups is 2.
A third switch is connected to these two impedance elements, and when the certain operation is performed, the relay controls the on/off and switching of the first, second, and third switches. A modem state control method, characterized in that the modem is configured to change the amplification degree of the modem, switch input/output impedance, and further change the impedance value of the balance net circuit.