JPS60214638A - Input and output circuit of modem for data transmission - Google Patents

Abstract

PURPOSE:To make data transmission compatible between a two-wire and a four- wire mode through a one-contact changeover switch by providing a gain control amplifier for level adjustment to the output side of a two-wire/four-wire changeover switch and forming a circuit which switches an unbalanced signal as it is. CONSTITUTION:When data is received from a domestic data center, an unbalanced up data signal is passed through a main attenuator 41, a contact (a) of the changeover switch 37, and gain control amplifier 42 and converted into a balanced signal, which is sent out to balanced lines 31A and 31B through a separator 32. On the other hand, when data from a foreign data center is received, the up data signal is supplied to an output transformer 56 through the main attenuator 41 and a contact (b) of the changeover switch 37 and converted into a balanced signal, which is sent out to balanced lines 48A and 48B. Thus, the amplifier 42 is installed at the output side of the switch 37 and the transformer 56 is used when data from the foreign data center is received to use only one contact for the switch 37.

Description

[Detailed Description of the Invention] [Field of Sedentary Work] The present invention relates to an input/output circuit of a modem for data transmission, and particularly relates to a captain system (Character AndP).
attern Telephone Access I
network system)
It is suitable for application to.

[Background technology and its problems]

The Captain System is a data transmission system that has been developed in recent years and supplies information consisting of character and graphic data prepared at a data center to an information receiving device installed at a specific subscriber station using a telephone line network. It is something that As shown in Figure 1, this system consists of telephone subscribers' telephones (1
) and the telephone exchange (2), a line switch (4) is installed at the terminal of the telephone line (3), and by switching this line switch (4), the data center (5)
The information receiving device (6) can receive and display character and graphic data (hereinafter referred to as data) transmitted from the telephone exchange (2) and the city 5th telephone exchange 11sji (3).

The information receiving device (6) has an adapter (7) connected to the line switch (4), and a modem (8) (referred to as a modem) installed in the adapter (7). To input information selection from the keyboard (9) via h! Then, the command signal issued by the signal processing circuit (10) is pasted on the turn leg (
3). At this time, the data that was not transmitted from the data center (5) is again supplied to the adapter (7) through the 11-channel line (3), and is re-attached to the Italian signal processing circuit (1) by the modem (8). 10) Follow the display and 1
2 is displayed on, for example, a television set (II).

Here, if a television set is used as a display device, text and graphic data can be transmitted over a general range by combining a commercial telephone and a television receiver. It is possible to realize an information transmission system that can be used for various purposes.

In the captain system, 'd1M fortune line (3)
is commonly used to send information selection command signals to the data center (5).
Figure 2 shows the band of the f-voice signal in order to send it to the upper line) and receive it to the data message receiver (6) (this loop is called the lower line). They are used by assigning frequency bands for uplink and downlink, respectively.

First, regarding the uplink, the information selection command signal SD is logical "
pSl ((frequency
-shiftkeying) is a digital modulation signal, and this is the upstream data signal. l) Cblt
/See] transmission speed.

On the other hand, for the downlink, the data RD is 2650
This is a digitally modulated signal using a vestigial sideband two-phase differential phase modulation method with a carrier of [11z), and this is sent out as a downlink data signal at a transmission speed of 3200 [bit/sec]. Here, the two-phase differential phase modulation signal is
For example, if the data RD is a series of logics as shown in Figure 3,
If the data R1 is composed of bits of 1 or 0, first a series of bits of the data R1) and bits of 1 and tfllrl-1 come as the differential signal 1)Ii'', as shown in FIG. 3(B). and difference signal No. 46 so that the inner bounds of the bit concerned are at a logic level that is the inversion of the inner bounds of the previous bit, and the difference signal 1) li' corresponding to the logic "0" bit of the data l1I). The bit is set to the same level as the inner bounds of its 811 bits. However, as shown in Fig. 4, this differential signal 1) is changed by changing the phase of the carrier by 1800 degrees when it is at the moon level, and the phase of the carrier is set to the reference phase, that is, 0°, and when it is at the commercial!'1' level. The gear is phase-modulated so that the two-phase difference position (11 modulation signals are obtained).

In this way, the information receiving device w from the data center (5)
(6) Reliable and fast transmission of data RD to 1.11
', and can be realized with a relatively simple configuration.

In this way, the uplink data signal and the downlink data m are transmitted using the ``Zubi 1 IM'' which is composed of two-wire balanced lines (15A) and (15B). There is. Therefore, in modem (8), the fifth
As shown in the figure, the balanced lines (17A) and (17B) introduced into the input/output circuit (1@) of the modem (8) are connected from the line switch (4) to the separator (1) with a no-brid coil configuration.
8), and the upstream data signal transmitted from the upstream data signal transmission circuit (19) via the unbalanced signal line (2) is converted into a balanced signal by the amplifier (21) and then passed through the separator (1B). At the same time, the downlink data signal arriving from the line switch (4) is separated by the separator (18) and then sent to the amplifier (22).
) is converted into an unbalanced signal and transmitted to the downlink data signal receiving circuit (24) via an unbalanced signal line (device), thus making it possible to reliably separate and process uplink and downlink data signals. Note that (25) is a balance circuit for the separator (18).

The above configuration has been used in domestic data transmission systems, but recently it has become possible to apply the captain system to international communications using satellite communication lines. However, in international communications, in order to prevent crosstalk between uplink and downlink, 4I/month is applied to each uplink and downlink.
It is standard practice to use a two-wire balanced line.

Therefore, in order to receive incoming data using an international communication line, it is necessary to transmit and receive 4g of the modem (8) of the information receiving device +1 (6) in a 4-wire format.

Like this [1;! ! The communication center is in the mouth/inside the room: jll
@' The transmission method is different from the 4 for international communication.
Is it possible to install the 1st generation cable for domestic communication separately from the 2nd type electricity transmission for domestic communication? If you want to receive the I-reports using your I-mail receiving device, you will have to arrange telephone lines in six states, which will inevitably result in an enormous amount of preparation.

During this time, as a way to decide whether to use 2 lines out of 4 telephone rounds, domestic
It is conceivable to provide the input/output circuit (y) with the configuration shown in the figure in the modem (8). In other words, m iL'1fi of the 4-way formula
10,000 equilibrium lines (31A) and (3
1B) is a separator (32) similar to that described above in FIG.
), and its down signal terminal (33A) and (33
1() is converted into an unbalanced signal by an amplifier (34) and provided to a downstream data signal receiving circuit (35). In addition, the upstream signal terminals (36A) and (36B) of the separator (32) are connected to the 211ffl terminals of the first and second contacts (38) and (39) of the 2-wire to 4-wire changeover switch (37).
Uplink data signal transmission circuit (40) via switching end a
An unbalanced output is provided via the main attenuator (4I) and the level adjustment gain control amplifier (42). Along with this, the upstream signal terminals (36A) and (36B) [are 2 wires -
A matching resistor (44) (e.g. 60Ω
) are connected.

Also, the other balanced line (48A) of the 4-win type telephone line
) and (48B) are connected to an upstream data signal output transformer (49) with a transformation ratio of 1:1, and the 70 Ping-Ji Sen end is connected to the 2i-4 through the level adjustment attenuator (50).
&I changeover switch (37) first and second contacts (38)
And (39) is connected to the 1st end of the 4-way battleship. Note that (5]) is the balance circuit of the separator (32).

In the configuration shown in FIG. 6, when data is received from a domestic data center and fcXA is used, the modem (8)'s 2-4 wire changeover switch (37) is set to 2&! Switch 0111 to end a. At this time, the unbalanced upstream data signal obtained from the two data signal transmitting circuits (40) is transmitted to the main attenuator (40).
1) '& given to the gain control amplifier (,12) through
Here, the first and second contacts of the 4-way switch (37) and the 2&! of (39) are converted to balanced output. II conversion
111 end a/separator (:sz), it is sent to one of the XF terminals (31A) and 1 (31B), thereby selecting the data to be received on the balanced line (31A).
) and the domestic data center connected to the central 11111 end of (3113).

The four data thus obtained at the data center are sent back to the separator (32) through the same balanced lines (31A) and (31B), converted into an unbalanced signal in the amplifier (shell), and sent to the downstream data signal receiving circuit (35). ), it is reproduced as a III image.

On the other hand, if you want to receive data from a data center overseas, switch the modem (8)'s 2-wire to 4-wire switch (
37) to the 4-wire switching side end 1). At this time, the unbalanced upstream data signal from the upstream data signal transmission circuit (4(+)
42), it is converted to a balanced output and then sent to the selector switch (
37), the first and second contacts (38) and (39), the level adjustment attenuator (50), the output transformer (49)
) through ten thousand equilibrium lines (48A) and (48B)
This causes balance lines (48A) and (4
8B) You can instruct the overseas data center to select the data you wish to receive via the international telephone line connected to one end of the center line.

Thus, the data obtained at the data center is Ehl
The other balanced line (31A) and (
31B) and is sent back to the rice separator (32) and amplifier (3
11), it is converted into an unbalanced signal and given to the downstream data signal receiving circuit (35), where it is expressed as an image. At this time, the upstream signal terminal (36) of the separator (32)
A) and (36B) have matching resistors (44) connected to 2 wires -4
It is connected via the third contact (43) of the line changeover switch (37), which prevents reflection and also connects the separator (32).
) operates as a simple coupling transformer.

With the configuration shown in Figure 6, the same information receiving device can be used to compatiblely receive data from a domestic telephone line and receive data from an international telephone line (Fi). However, This &) configuration is designed to switch the balanced signal in order to switch between international communication and domestic communication.
4 #+j changeover switch (37) has too many contacts. -Also, when transmitting uplink data signals, in a two-wire system, a separator (32) 't' jl! In contrast, in the 4-wire system, the signal is sent to the equilibrium lines (48A) and (48B) without skipping the splitter (32). , a level adjustment attenuator (50) is required to equalize the levels of the input and output signals, which has the unavoidable disadvantage that the overall configuration becomes complicated. Incidentally, the level adjustment first gain control amplifier (42) is provided to compensate for the attenuation (approximately -4 dB) given by the separator (32) when transmitting the upper side data signal in the case of a two-wire system. However, when using a 4-wire system, the reduction in output power (49) is relatively small (approximately -1 dB), so the reduction in P
This is because it is necessary to attenuate the difference in the i amount (approximately -3 dB) using the level adjustment attenuator (50).

[Purpose of the invention]

In consideration of the above points, the present invention provides a data transmission modem that can perform two-wire data transmission and four-wire data transmission compatiblely with a simpler configuration than the configuration shown in FIG. This is what I am trying to propose.

[Summary of the invention]

In order to achieve such an object, the present invention is connected to a telephone line consisting of a first balanced line and transmits a downlink data signal coming from the first balanced line to a downlink data signal receiving circuit connected to an input signal end. a separator that sends the upstream data signal that arrives at the output signal end to the first balanced line; and a 2i cutting end or 4-wire switching switch Q: A 2-wire to 4-wire switching switch that switches to M and outputs it, and when an upstream data signal is output to the 2-wire switching side end of this 2-4-wire switching switch, the upstream data signal is output to the Benefit from attenuation! A gain amplifier for level adjustment, and a 2#
4-wire switching of J+-4 pure changeover switch (when an upstream data signal is output to the ill end), an unbalanced-balanced converter that outputs the yuri data signal as a balanced output to the telephone line consisting of the second balanced line. equip

〔Example〕

Below, the corresponding part to Figure 6 is shown with No. 9 of the same figure.
Let us illustrate an example of the invention with reference to the figures. In this case 2 lines -
The 4-wire selector switch (37) is connected to the 1161 contact (55
), and its input terminal is connected to an upstream data signal transmission circuit (40
) Main attenuator 1 installed at 1111
(41), and the unbalanced upstream data obtained at the two-wire switching $111 terminal a is converted into a balanced signal by the signal/J's'/Novel adjustment gain control amplifier (42). It is connected to the upstream signal terminals (36A) and (36B) of the separator (32), and the unbalanced upstream data signal obtained from the 4-wire switching side end bK is connected to the output transformer (b+).
It is connected to one of the balance lines (48A) and (48B) via.

Here, the output of the main attenuator (41) remains an unbalanced signal, and the output transformer (56) operates as an unbalanced-balanced converter that converts this unbalanced signal into a balanced signal.

In the configuration shown in FIG. 7, when data is to be received from a domestic data center, the 2-wire/4-wire switching switch (37) of the modem (8) is switched to the 2-wire switching end a.

At this time, the unbalanced upstream data signal from the upstream data transmission circuit (40) is not applied to the gain control amplifier (42) through the main attenuator (41) and the changeover switch (55), and is converted into a balanced signal. is sent to a pair of balance lines (31A) and (31B) via a separator (32),
This allows the domestic data center to be instructed to select the data it wishes to receive in the same manner as described above with reference to FIG. The data thus obtained at the data center is sent back to the separator (32) through the same balanced lines (31A) and (31B), converted into a balanced signal by the amplifier (34), and then provided to the downstream data signal receiving circuit (35). and reproduced as an image.

At this time, the 111 fl unit (32
The attenuation provided in the level adjustment gain control amplifier (42) is compensated for by the level adjustment gain control amplifier (42).

On the other hand, when receiving data from a data center overseas, the modem (8)'s 2-wire-4 pure switch (3
7) is switched to 4-way switching (Ill end). At this time, the "elementary data signal" from the upstream data signal transmission circuit (40) is sent to the output transformer (51i) through the main attenuator (41) and the changeover switch (37). The data obtained from the data center outside I'jjl is transmitted to the other balanced line (31
A) and (31B'), the signal is returned to the divider 1 unit (32), converted into an unbalanced signal by the amplifier (34), and then given to the downstream data signal receiving circuit (35).
It is reproduced as a IIl image.

However, at this time, the high level data signal is connected to the main attenuator (4
1) Since the output signal is directly applied to the output attenuator (56) without passing through the level adjustment attenuator (42), it is not subjected to level adjustment and the relatively small attenuation provided by the output attenuation (56) is applied! (approximately -1d13), thus matching the signal level in the two-wire system. In the case of a two-wire system, the separator (32) provides attenuation of -4 dB, whereas this is compensated by +3 dB with the level filter (42). Specifically, the signal level of the upstream data signal sent to the line balance lines (31A) and (31B) is set to -1dll.

In the embodiment shown in FIG. 7, the upstream data signal of the 4-wire switching terminal of the 2-wire-4-wire switching switch (37) is connected to the balanced lines (48A) and (48B), so that it is an unbalanced-balanced type. Although the output transformer (56) made of a transformer is used, the same effects as in the above case can be obtained even if an unbalanced-balanced converter is used in general.

〔Effect of the invention〕

As described above, according to the present invention, when transmitting and receiving uplink data signals and downlink data signals using a 4-wire T-talk line,
This can be realized by a simple configuration that only requires the minimum necessary elements compared to the configuration using the two-wire m-Ayu line. Incidentally, according to the configuration shown in FIG. 6, after adjusting the gain of the upstream data signal using the level self-adjusting gain control amplifier (42) and converting it into a balanced signal, the 2-wire -4*j! Changeover switch (37
), when switching to a 4-wire system, a level compensation attenuator (50) and a matching resistor (44) are required, as well as a selector switch (37).
), three contacts (38), C mountain), and <43> are required, but in the present invention, level 1! I-control gain control amplifier (42) to 2-wire to 4-win switching switch (37)
Since the unbalanced signal is switched as it is by providing it at the output terminal 1 of the switch 1, it is possible to simplify the configuration by simply providing a changeover switch (37) having one contact (b5).

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional captain system.
Figure 2 is a curve diagram explaining the upstream and downstream data signals, and Figures 3 and 4 are detailed dR data signals.
Figure 5 is a connection diagram showing the detailed configuration of the modem in Figure 1, Figure 6 is a connection diagram showing possible input/output circuits for 2-wire to 4-wire switching. ,
FIG. 7 is a connection diagram showing an example of the input/output circuit of the data transmission modem according to the present invention. (1)...Telephone, (2)...Telephone exchange, (3)
...Telephone line, (4)...Line switch, (5).
...Data center, (6)...-Information receiving device, (7)
... adapter, (8) ... modem, (9) ... keyboard, (10) ... signal processing circuit, (11) ...
・Television set, (30)...Input/output circuit, (
15A), (15B). (17A), (17B)... Equilibrium line, (
18)...Separator, (19)...Uplink data signal transmission circuit, (20), (Z()...Unbalanced signal line,
(24)...lower data signal receiving circuit, (δ)...
Balance circuit, (32)...separator, (34)... amplifier, (a)... downlink data signal receiving circuit, (37)...
・・2 wire-4 set changeover switch, (38), (39)
, (43) , (55) =・Contact, (4(])
...Uplink data signal transmission circuit, (41)...Main attenuator, (-12)...Level adjustment attenuator, (49). (56)...Transformer for outputting data signals.

Claims (1)

[Claims] A downlink data signal connected to a telephone line consisting of a first balanced line and arriving from the first balanced line is applied to a downlink data signal receiving circuit connected to an input signal end, and an output signal is a separator for sending the upstream data signal arriving at the end to the first balanced line;
2 wires output by switching to 1 end or 4 wire switching end
The 4 wire changeover switch and this 2 wire - 4 wire changeover switch
Line switching (gain control for level adjustment when the above data signal is output to the ill end, compensates the gain of the above data signal by the attenuation of the separator and supplies it as a balanced output to the output signal end of the separator) Unbalanced-balanced, when the upstream data signal is output to the amplifier and the 4-win switching end of the 2-wire to 4-wire switch, the upstream data signal is given as a balanced output to the telephone line, which is a second balanced line. An input/output circuit for a modem for data transmission, characterized in that it shares a converter.